feat: implement link embed functionality to enhance message previews with metadata and thumbnails

src/EchoHub.Server/Data/EchoHubDbContext.cs

@@ -59,6 +59,7 @@ public class EchoHubDbContext : DbContext
             entity.Property(m => m.SenderUsername).IsRequired().HasMaxLength(50);
             entity.Property(m => m.AttachmentUrl).HasMaxLength(500);
             entity.Property(m => m.AttachmentFileName).HasMaxLength(255);
+            entity.Property(m => m.EmbedJson).HasMaxLength(8000);
         });
 
         modelBuilder.Entity<ChannelMembership>(entity =>

src/EchoHub.Server/Data/Migrations/20260219201704_AddMessageEmbed.Designer.cs

@@ -0,0 +1,264 @@
+// <auto-generated />
+using System;
+using EchoHub.Server.Data;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Infrastructure;
+using Microsoft.EntityFrameworkCore.Migrations;
+using Microsoft.EntityFrameworkCore.Storage.ValueConversion;
+
+#nullable disable
+
+namespace EchoHub.Server.Data.Migrations
+{
+    [DbContext(typeof(EchoHubDbContext))]
+    [Migration("20260219201704_AddMessageEmbed")]
+    partial class AddMessageEmbed
+    {
+        /// <inheritdoc />
+        protected override void BuildTargetModel(ModelBuilder modelBuilder)
+        {
+#pragma warning disable 612, 618
+            modelBuilder.HasAnnotation("ProductVersion", "10.0.3");
+
+            modelBuilder.Entity("EchoHub.Core.Models.Channel", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("TEXT");
+
+                    b.Property<long>("CreatedAt")
+                        .HasColumnType("INTEGER");
+
+                    b.Property<Guid>("CreatedByUserId")
+                        .HasColumnType("TEXT");
+
+                    b.Property<bool>("IsPublic")
+                        .HasColumnType("INTEGER");
+
+                    b.Property<string>("Name")
+                        .IsRequired()
+                        .HasMaxLength(100)
+                        .HasColumnType("TEXT");
+
+                    b.Property<string>("Topic")
+                        .HasMaxLength(500)
+                        .HasColumnType("TEXT");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("Name")
+                        .IsUnique();
+
+                    b.ToTable("Channels");
+                });
+
+            modelBuilder.Entity("EchoHub.Core.Models.ChannelMembership", b =>
+                {
+                    b.Property<Guid>("UserId")
+                        .HasColumnType("TEXT");
+
+                    b.Property<Guid>("ChannelId")
+                        .HasColumnType("TEXT");
+
+                    b.Property<long>("JoinedAt")
+                        .HasColumnType("INTEGER");
+
+                    b.HasKey("UserId", "ChannelId");
+
+                    b.HasIndex("ChannelId");
+
+                    b.HasIndex("UserId");
+
+                    b.ToTable("ChannelMemberships");
+                });
+
+            modelBuilder.Entity("EchoHub.Core.Models.Message", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("TEXT");
+
+                    b.Property<string>("AttachmentFileName")
+                        .HasMaxLength(255)
+                        .HasColumnType("TEXT");
+
+                    b.Property<string>("AttachmentUrl")
+                        .HasMaxLength(500)
+                        .HasColumnType("TEXT");
+
+                    b.Property<Guid>("ChannelId")
+                        .HasColumnType("TEXT");
+
+                    b.Property<string>("Content")
+                        .IsRequired()
+                        .HasMaxLength(2000)
+                        .HasColumnType("TEXT");
+
+                    b.Property<string>("EmbedJson")
+                        .HasMaxLength(8000)
+                        .HasColumnType("TEXT");
+
+                    b.Property<Guid>("SenderUserId")
+                        .HasColumnType("TEXT");
+
+                    b.Property<string>("SenderUsername")
+                        .IsRequired()
+                        .HasMaxLength(50)
+                        .HasColumnType("TEXT");
+
+                    b.Property<long>("SentAt")
+                        .HasColumnType("INTEGER");
+
+                    b.Property<int>("Type")
+                        .HasColumnType("INTEGER");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("ChannelId");
+
+                    b.HasIndex("SentAt");
+
+                    b.ToTable("Messages");
+                });
+
+            modelBuilder.Entity("EchoHub.Core.Models.RefreshToken", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("TEXT");
+
+                    b.Property<long>("CreatedAt")
+                        .HasColumnType("INTEGER");
+
+                    b.Property<long>("ExpiresAt")
+                        .HasColumnType("INTEGER");
+
+                    b.Property<long?>("RevokedAt")
+                        .HasColumnType("INTEGER");
+
+                    b.Property<string>("TokenHash")
+                        .IsRequired()
+                        .HasMaxLength(128)
+                        .HasColumnType("TEXT");
+
+                    b.Property<Guid>("UserId")
+                        .HasColumnType("TEXT");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("TokenHash");
+
+                    b.HasIndex("UserId");
+
+                    b.ToTable("RefreshTokens");
+                });
+
+            modelBuilder.Entity("EchoHub.Core.Models.User", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("TEXT");
+
+                    b.Property<string>("AvatarAscii")
+                        .HasMaxLength(10000)
+                        .HasColumnType("TEXT");
+
+                    b.Property<string>("Bio")
+                        .HasMaxLength(500)
+                        .HasColumnType("TEXT");
+
+                    b.Property<long>("CreatedAt")
+                        .HasColumnType("INTEGER");
+
+                    b.Property<string>("DisplayName")
+                        .HasMaxLength(100)
+                        .HasColumnType("TEXT");
+
+                    b.Property<bool>("IsBanned")
+                        .HasColumnType("INTEGER");
+
+                    b.Property<bool>("IsMuted")
+                        .HasColumnType("INTEGER");
+
+                    b.Property<long>("LastSeenAt")
+                        .HasColumnType("INTEGER");
+
+                    b.Property<long?>("MutedUntil")
+                        .HasColumnType("INTEGER");
+
+                    b.Property<string>("NicknameColor")
+                        .HasMaxLength(7)
+                        .HasColumnType("TEXT");
+
+                    b.Property<string>("PasswordHash")
+                        .IsRequired()
+                        .HasColumnType("TEXT");
+
+                    b.Property<int>("Role")
+                        .HasColumnType("INTEGER");
+
+                    b.Property<int>("Status")
+                        .HasColumnType("INTEGER");
+
+                    b.Property<string>("StatusMessage")
+                        .HasMaxLength(100)
+                        .HasColumnType("TEXT");
+
+                    b.Property<string>("Username")
+                        .IsRequired()
+                        .HasMaxLength(50)
+                        .HasColumnType("TEXT");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("Username")
+                        .IsUnique();
+
+                    b.ToTable("Users");
+                });
+
+            modelBuilder.Entity("EchoHub.Core.Models.ChannelMembership", b =>
+                {
+                    b.HasOne("EchoHub.Core.Models.Channel", null)
+                        .WithMany()
+                        .HasForeignKey("ChannelId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.HasOne("EchoHub.Core.Models.User", null)
+                        .WithMany()
+                        .HasForeignKey("UserId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+                });
+
+            modelBuilder.Entity("EchoHub.Core.Models.Message", b =>
+                {
+                    b.HasOne("EchoHub.Core.Models.Channel", "Channel")
+                        .WithMany("Messages")
+                        .HasForeignKey("ChannelId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.Navigation("Channel");
+                });
+
+            modelBuilder.Entity("EchoHub.Core.Models.RefreshToken", b =>
+                {
+                    b.HasOne("EchoHub.Core.Models.User", "User")
+                        .WithMany()
+                        .HasForeignKey("UserId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.Navigation("User");
+                });
+
+            modelBuilder.Entity("EchoHub.Core.Models.Channel", b =>
+                {
+                    b.Navigation("Messages");
+                });
+#pragma warning restore 612, 618
+        }
+    }
+}

src/EchoHub.Server/Data/Migrations/20260219201704_AddMessageEmbed.cs

@@ -0,0 +1,29 @@
+using Microsoft.EntityFrameworkCore.Migrations;
+
+#nullable disable
+
+namespace EchoHub.Server.Data.Migrations
+{
+    /// <inheritdoc />
+    public partial class AddMessageEmbed : Migration
+    {
+        /// <inheritdoc />
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.AddColumn<string>(
+                name: "EmbedJson",
+                table: "Messages",
+                type: "TEXT",
+                maxLength: 8000,
+                nullable: true);
+        }
+
+        /// <inheritdoc />
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropColumn(
+                name: "EmbedJson",
+                table: "Messages");
+        }
+    }
+}

src/EchoHub.Server/Data/Migrations/EchoHubDbContextModelSnapshot.cs

@@ -91,6 +91,10 @@ namespace EchoHub.Server.Data.Migrations
                         .HasMaxLength(2000)
                         .HasColumnType("TEXT");
 
+                    b.Property<string>("EmbedJson")
+                        .HasMaxLength(8000)
+                        .HasColumnType("TEXT");
+
                     b.Property<Guid>("SenderUserId")
                         .HasColumnType("TEXT");