Add ChapterKind for front/back matter chapters

Chapters can now be marked FrontMatter/Body/BackMatter. Number stays
the manuscript sort key for every chapter; the author-facing display
number is now computed per-request as the chapter's ordinal among
Body chapters only, so a foreword or afterword no longer shifts the
numbering of the rest of the book. Surfaced through the API, agent
toolset, and import toolset.

tests/Novelly.Api.Tests/ChapterServiceTests.cs

@@ -78,4 +78,62 @@ public class ChapterServiceTests : ServiceTestFixture
     [Test]
     public async Task Deleting_a_missing_chapter_returns_false_rather_than_throwing() =>
         Assert.That(await Chapters.DeleteAsync(Guid.NewGuid()), Is.False);
+
+    [Test]
+    public async Task A_chapter_defaults_to_a_body_chapter()
+    {
+        var chapter = await Chapters.CreateAsync(_novelId, new CreateChapterRequest("Landfall"));
+
+        Assert.That(chapter!.Kind, Is.EqualTo(ChapterKind.Body));
+    }
+
+    [Test]
+    public async Task Front_matter_does_not_consume_a_chapter_number()
+    {
+        var foreword = await Chapters.CreateAsync(_novelId, new CreateChapterRequest("Foreword", Number: 1, Kind: ChapterKind.FrontMatter));
+        var first = await Chapters.CreateAsync(_novelId, new CreateChapterRequest("Landfall", Number: 2));
+        var second = await Chapters.CreateAsync(_novelId, new CreateChapterRequest("The Harbour", Number: 3));
+
+        var displayNumbers = ChapterNumbering.DisplayNumbers(await Chapters.ListAsync(_novelId));
+
+        Assert.Multiple(() =>
+        {
+            Assert.That(displayNumbers.ContainsKey(foreword!.Id), Is.False);
+            Assert.That(displayNumbers[first!.Id], Is.EqualTo(1));
+            Assert.That(displayNumbers[second!.Id], Is.EqualTo(2));
+        });
+    }
+
+    [Test]
+    public async Task Back_matter_is_listed_last_but_carries_no_chapter_number()
+    {
+        var body = await Chapters.CreateAsync(_novelId, new CreateChapterRequest("Landfall", Number: 1));
+        var afterword = await Chapters.CreateAsync(_novelId, new CreateChapterRequest("Afterword", Number: 2, Kind: ChapterKind.BackMatter));
+
+        var afterwordDisplayNumber = await Chapters.DisplayNumberAsync(afterword!);
+        var bodyDisplayNumber = await Chapters.DisplayNumberAsync(body!);
+
+        Assert.Multiple(() =>
+        {
+            Assert.That(afterwordDisplayNumber, Is.Null);
+            Assert.That(bodyDisplayNumber, Is.EqualTo(1));
+        });
+    }
+
+    [Test]
+    public async Task Changing_a_chapter_to_front_matter_drops_it_from_the_chapter_count()
+    {
+        var chapter = await Chapters.CreateAsync(_novelId, new CreateChapterRequest("Prologue", Number: 1));
+        var other = await Chapters.CreateAsync(_novelId, new CreateChapterRequest("Landfall", Number: 2));
+
+        var updated = await Chapters.UpdateAsync(chapter!.Id, new UpdateChapterRequest(Kind: ChapterKind.FrontMatter));
+        var updatedDisplayNumber = await Chapters.DisplayNumberAsync(updated!);
+        var otherDisplayNumber = await Chapters.DisplayNumberAsync(other!);
+
+        Assert.Multiple(() =>
+        {
+            Assert.That(updatedDisplayNumber, Is.Null);
+            Assert.That(otherDisplayNumber, Is.EqualTo(1));
+        });
+    }
 }