Add GitHub-style activity contribution graph

Record create/update/delete events across novel content (chapters, beats,
characters, arc stages, tags, locations, questions) into an append-only
ActivityEvent log, aggregate by UTC day, and surface as a heatmap on the
novels list and each novel's dashboard. Backfills history from existing
CreatedAt timestamps on first boot after the migration.

tests/Novelly.Api.Tests/ActivityTests.cs

@@ -0,0 +1,127 @@
+using Microsoft.EntityFrameworkCore;
+using Novelly.Api.Activity;
+using Novelly.Api.Beats;
+using Novelly.Api.Chapters;
+using Novelly.Api.Novels;
+using Novelly.Api.Users;
+
+namespace Novelly.Api.Tests;
+
+[TestFixture]
+public class ActivityTests : ServiceTestFixture
+{
+    private Guid AsNewUser(GlobalRole globalRole)
+    {
+        var user = new NovellyUser
+        {
+            Id = Guid.NewGuid(),
+            UserName = $"{Guid.NewGuid()}@novelly.test",
+            Email = $"{Guid.NewGuid()}@novelly.test",
+            DisplayName = "Test User",
+            GlobalRole = globalRole
+        };
+        Db.Context.Users.Add(user);
+        Db.Context.SaveChanges();
+
+        UserContext.UserId = user.Id;
+        UserContext.GlobalRole = globalRole;
+        return user.Id;
+    }
+
+    [Test]
+    public async Task Writing_prose_records_the_word_delta_for_that_day()
+    {
+        var novel = await Novels.CreateAsync(new CreateNovelRequest("The Salt Road"));
+        var chapter = await Chapters.CreateAsync(novel.Id, new CreateChapterRequest("Landfall"));
+
+        await Chapters.UpdateAsync(chapter!.Id, new UpdateChapterRequest(Prose: "one two three four five"));
+
+        var calendar = await Activity.GetForNovelAsync(novel.Id, days: 7);
+
+        Assert.That(calendar.Days.Sum(d => d.Words), Is.EqualTo(5));
+    }
+
+    [Test]
+    public async Task Editing_a_beat_records_one_edit_not_two()
+    {
+        var novel = await Novels.CreateAsync(new CreateNovelRequest("The Salt Road"));
+        var chapter = await Chapters.CreateAsync(novel.Id, new CreateChapterRequest("Landfall"));
+        var beat = await Beats.CreateAsync(chapter!.Id, new CreateBeatRequest("She finds the map"));
+
+        await Beats.UpdateAsync(beat!.Id, new UpdateBeatRequest(WhatHappened: "She finds the map under the floorboards."));
+
+        var beatEvents = await Db.Context.ActivityEvents.CountAsync(e => e.EntityKind == ActivityEntityKind.Beat);
+        var chapterEvents = await Db.Context.ActivityEvents.CountAsync(e => e.EntityKind == ActivityEntityKind.Chapter);
+
+        Assert.Multiple(() =>
+        {
+            Assert.That(beatEvents, Is.EqualTo(2));
+            Assert.That(chapterEvents, Is.EqualTo(1));
+        });
+    }
+
+    [Test]
+    public async Task Deleting_a_chapter_records_a_negative_word_delta()
+    {
+        var novel = await Novels.CreateAsync(new CreateNovelRequest("The Salt Road"));
+        var chapter = await Chapters.CreateAsync(novel.Id, new CreateChapterRequest("Landfall", Prose: "one two three"));
+
+        await Chapters.DeleteAsync(chapter!.Id);
+
+        var calendar = await Activity.GetForNovelAsync(novel.Id, days: 7);
+
+        Assert.That(calendar.Days.Sum(d => d.Words), Is.EqualTo(0));
+    }
+
+    [Test]
+    public async Task The_calendar_groups_multiple_edits_into_one_day()
+    {
+        var novel = await Novels.CreateAsync(new CreateNovelRequest("The Salt Road"));
+        var chapter = await Chapters.CreateAsync(novel.Id, new CreateChapterRequest("Landfall"));
+
+        await Chapters.UpdateAsync(chapter!.Id, new UpdateChapterRequest(Summary: "First pass"));
+        await Chapters.UpdateAsync(chapter.Id, new UpdateChapterRequest(Summary: "Second pass"));
+
+        var calendar = await Activity.GetForNovelAsync(novel.Id, days: 7);
+
+        Assert.Multiple(() =>
+        {
+            Assert.That(calendar.Days, Has.Count.EqualTo(1));
+            Assert.That(calendar.Days[0].Edits, Is.EqualTo(4));
+        });
+    }
+
+    [Test]
+    public async Task The_calendar_omits_days_with_no_activity()
+    {
+        var novel = await Novels.CreateAsync(new CreateNovelRequest("The Salt Road"));
+
+        var calendar = await Activity.GetForNovelAsync(novel.Id, days: 7);
+
+        Assert.That(calendar.Days, Has.Count.EqualTo(1));
+    }
+
+    [Test]
+    public async Task The_calendar_excludes_novels_the_user_cannot_read()
+    {
+        var novel = await Novels.CreateAsync(new CreateNovelRequest("Someone Else's Novel"));
+
+        AsNewUser(GlobalRole.Writer);
+        await Novels.CreateAsync(new CreateNovelRequest("My Own Novel"));
+
+        var calendar = await Activity.GetForCurrentUserAsync(days: 7);
+
+        Assert.That(calendar.TotalEdits, Is.EqualTo(1));
+    }
+
+    [Test]
+    public async Task Deleting_a_novel_removes_its_activity_events()
+    {
+        var novel = await Novels.CreateAsync(new CreateNovelRequest("The Salt Road"));
+        await Chapters.CreateAsync(novel.Id, new CreateChapterRequest("Landfall"));
+
+        await Novels.DeleteAsync(novel.Id);
+
+        Assert.That(await Db.Context.ActivityEvents.CountAsync(e => e.NovelId == novel.Id), Is.EqualTo(0));
+    }
+}