Use springio/antora-extensions

docs/spring-authorization-server-docs.gradle

@@ -10,14 +10,11 @@ version = project.rootProject.version
 sourceCompatibility = "17"
 
 antora {
-	playbook = "cached-antora-playbook.yml"
-	playbookProvider {
-		repository = "spring-projects/spring-authorization-server"
-		branch = "docs-build"
-		path = "lib/antora/templates/per-branch-antora-playbook.yml"
-		checkLocalBranch = true
-	}
 	options = [clean: true, fetch: !project.gradle.startParameter.offline, stacktrace: true]
+	environment = [
+		'BUILD_REFNAME': 'HEAD',
+		'BUILD_VERSION': project.version,
+	]
 }
 
 tasks.named("generateAntoraYml") {