[FA-27] Bookmark implementation

FictionArchive.Service.UserNovelDataService/Services/UserNovelDataServiceDbContext.cs

@@ -1,11 +1,35 @@
 using FictionArchive.Service.Shared.Services.Database;
+using FictionArchive.Service.UserNovelDataService.Models.Database;
 using Microsoft.EntityFrameworkCore;
 
 namespace FictionArchive.Service.UserNovelDataService.Services;
 
 public class UserNovelDataServiceDbContext : FictionArchiveDbContext
 {
+    public DbSet<User> Users { get; set; }
+    public DbSet<Bookmark> Bookmarks { get; set; }
+
     public UserNovelDataServiceDbContext(DbContextOptions options, ILogger<UserNovelDataServiceDbContext> logger) : base(options, logger)
     {
     }
-}
+
+    protected override void OnModelCreating(ModelBuilder modelBuilder)
+    {
+        base.OnModelCreating(modelBuilder);
+
+        modelBuilder.Entity<Bookmark>(entity =>
+        {
+            // Unique constraint: one bookmark per chapter per user
+            entity.HasIndex(b => new { b.UserId, b.ChapterId }).IsUnique();
+
+            // Index for efficient "get bookmarks for novel" queries
+            entity.HasIndex(b => new { b.UserId, b.NovelId });
+
+            // User relationship
+            entity.HasOne(b => b.User)
+                .WithMany()
+                .HasForeignKey(b => b.UserId)
+                .OnDelete(DeleteBehavior.Cascade);
+        });
+    }
+}