[FA-27] Need to test events but seems to mostly work

FictionArchive.Service.UserNovelDataService/Services/EventHandlers/NovelCreatedEventHandler.cs

@@ -0,0 +1,36 @@
+using FictionArchive.Service.Shared.Services.EventBus;
+using FictionArchive.Service.UserNovelDataService.Models.Database;
+using FictionArchive.Service.UserNovelDataService.Models.IntegrationEvents;
+using Microsoft.EntityFrameworkCore;
+
+namespace FictionArchive.Service.UserNovelDataService.Services.EventHandlers;
+
+public class NovelCreatedEventHandler : IIntegrationEventHandler<NovelCreatedEvent>
+{
+    private readonly UserNovelDataServiceDbContext _dbContext;
+    private readonly ILogger<NovelCreatedEventHandler> _logger;
+
+    public NovelCreatedEventHandler(
+        UserNovelDataServiceDbContext dbContext,
+        ILogger<NovelCreatedEventHandler> logger)
+    {
+        _dbContext = dbContext;
+        _logger = logger;
+    }
+
+    public async Task Handle(NovelCreatedEvent @event)
+    {
+        var exists = await _dbContext.Novels.AnyAsync(n => n.Id == @event.NovelId);
+        if (exists)
+        {
+            _logger.LogDebug("Novel {NovelId} already exists, skipping", @event.NovelId);
+            return;
+        }
+
+        var novel = new Novel { Id = @event.NovelId };
+        _dbContext.Novels.Add(novel);
+        await _dbContext.SaveChangesAsync();
+
+        _logger.LogInformation("Created novel stub for {NovelId}", @event.NovelId);
+    }
+}