feat(emblem): /emblem/favorite accept-only (persistence deferred)

SVSim.UnitTests/Controllers/EmblemControllerFavoriteTests.cs

@@ -0,0 +1,37 @@
+using System.Net;
+using System.Text;
+using NUnit.Framework;
+using SVSim.UnitTests.Infrastructure;
+
+namespace SVSim.UnitTests.Controllers;
+
+public class EmblemControllerFavoriteTests
+{
+    [Test]
+    public async Task Favorite_accepts_add_and_remove_lists()
+    {
+        using var factory = new SVSimTestFactory();
+        long viewerId = await factory.SeedViewerAsync(tutorialState: 0);
+        using var client = factory.CreateAuthenticatedClient(viewerId);
+
+        var requestJson = """{"favorite_add":["100","101"],"favorite_remove":["200"],"viewer_id":"0","steam_id":0,"steam_session_ticket":""}""";
+        var response = await client.PostAsync("/emblem/favorite",
+            new StringContent(requestJson, Encoding.UTF8, "application/json"));
+
+        Assert.That(response.StatusCode, Is.EqualTo(HttpStatusCode.OK));
+    }
+
+    [Test]
+    public async Task Favorite_accepts_empty_lists()
+    {
+        using var factory = new SVSimTestFactory();
+        long viewerId = await factory.SeedViewerAsync(tutorialState: 0);
+        using var client = factory.CreateAuthenticatedClient(viewerId);
+
+        var requestJson = """{"favorite_add":[],"favorite_remove":[],"viewer_id":"0","steam_id":0,"steam_session_ticket":""}""";
+        var response = await client.PostAsync("/emblem/favorite",
+            new StringContent(requestJson, Encoding.UTF8, "application/json"));
+
+        Assert.That(response.StatusCode, Is.EqualTo(HttpStatusCode.OK));
+    }
+}