feat(11.1-04): add the Database section and the core Services pages

- docs/database: models, migrations, queries and pagination, relations,
  casts and validation, attachments and transactions (lagoon.Transaction,
  lagoon.AfterCommit, nested savepoints, lagoon.OnDatabase)
- docs/services: configuration, events, routing with auth groups, rate
  limiting, authentication, the OAuth server, mail and localization
- runnable Examples for lagoon, attach, compass, surf, wire, bouncer,
  wristband, postcard, phrasebook and festival; lagoon TestDocs* regions
  run on the package's Postgres harness through DocsDB
- 15 new required pages

modules/festival/example_test.go

@@ -33,3 +33,60 @@ func ExampleBus_Fire() {
 	// notify subscribers of Hello
 	// index Hello
 }
+
+// PostFormExtended gathers extra fields other plugins add to the post form.
+type PostFormExtended struct {
+	fields map[string]any
+}
+
+func (e *PostFormExtended) Collected() map[string]any { return e.fields }
+
+func ExampleBus_Collect() {
+	bus := festival.New()
+	bus.Listen("acme.seo", func(ctx context.Context, e *PostFormExtended) error {
+		e.fields = map[string]any{"meta_title": "text"}
+		return nil
+	})
+	bus.Listen("acme.gallery", func(ctx context.Context, e *PostFormExtended) error {
+		e.fields = map[string]any{"cover": "fileupload"}
+		return nil
+	})
+
+	fields, err := bus.Collect(context.Background(), &PostFormExtended{})
+	fmt.Println(fields, err)
+	// Output: map[cover:fileupload meta_title:text] <nil>
+}
+
+// SlugResolving asks plugins to resolve a URL slug; the first one that
+// knows it handles the event.
+type SlugResolving struct {
+	Slug  string
+	Found string
+}
+
+func (e *SlugResolving) IsHandled() bool { return e.Found != "" }
+
+func ExampleBus_UntilHandled() {
+	bus := festival.New()
+	bus.ListenPriority("acme.pages", 10, func(ctx context.Context, e *SlugResolving) error {
+		if e.Slug == "about" {
+			e.Found = "page"
+		}
+		return nil
+	})
+	bus.Listen("acme.blog", func(ctx context.Context, e *SlugResolving) error {
+		fmt.Println("acme.blog asked for", e.Slug)
+		e.Found = "post"
+		return nil
+	})
+
+	for _, slug := range []string{"about", "hello-world"} {
+		e := &SlugResolving{Slug: slug}
+		handled, err := bus.UntilHandled(context.Background(), e)
+		fmt.Println(slug, handled, e.Found, err)
+	}
+	// Output:
+	// about true page <nil>
+	// acme.blog asked for hello-world
+	// hello-world true post <nil>
+}