feat(bookstack-api-dd0): implement ChaptersService List, Get, ListAll

Implement ChaptersService with List, Get, and ListAll iterator.
Add mock server tests.

chapters_test.go

@@ -0,0 +1,62 @@
+package bookstack
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"net/http"
+	"testing"
+)
+
+func TestChaptersService_List(t *testing.T) {
+	c := testClient(t, func(w http.ResponseWriter, r *http.Request) {
+		if r.URL.Path != "/api/chapters" {
+			t.Errorf("path = %s, want /api/chapters", r.URL.Path)
+		}
+		json.NewEncoder(w).Encode(map[string]any{
+			"data":  []map[string]any{{"id": 1, "name": "Ch 1", "book_id": 1}},
+			"total": 1,
+		})
+	})
+
+	chapters, err := c.Chapters.List(context.Background(), nil)
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if len(chapters) != 1 {
+		t.Fatalf("got %d chapters, want 1", len(chapters))
+	}
+}
+
+func TestChaptersService_Get(t *testing.T) {
+	c := testClient(t, func(w http.ResponseWriter, r *http.Request) {
+		if r.URL.Path != "/api/chapters/3" {
+			t.Errorf("path = %s, want /api/chapters/3", r.URL.Path)
+		}
+		json.NewEncoder(w).Encode(map[string]any{
+			"id": 3, "name": "Chapter Three", "book_id": 1,
+		})
+	})
+
+	ch, err := c.Chapters.Get(context.Background(), 3)
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if ch.Name != "Chapter Three" {
+		t.Errorf("Name = %q, want %q", ch.Name, "Chapter Three")
+	}
+}
+
+func TestChaptersService_Get_NotFound(t *testing.T) {
+	c := testClient(t, func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusNotFound)
+		json.NewEncoder(w).Encode(map[string]any{
+			"error": map[string]string{"message": "Chapter not found"},
+		})
+	})
+
+	_, err := c.Chapters.Get(context.Background(), 999)
+	if !errors.Is(err, ErrNotFound) {
+		t.Errorf("expected ErrNotFound, got %v", err)
+	}
+}