Include Kotlin API documentation in the documentation site

Closes gh-40692

spring-boot-project/spring-boot-docs/build.gradle

@@ -54,6 +54,9 @@ dependencies {
 	configurationProperties(project(path: ":spring-boot-project:spring-boot-test-autoconfigure", configuration: "configurationPropertiesMetadata"))
 	configurationProperties(project(path: ":spring-boot-project:spring-boot-testcontainers", configuration: "configurationPropertiesMetadata"))
 
+	dokkatoo(project(path: ":spring-boot-project:spring-boot"))
+	dokkatoo(project(path: ":spring-boot-project:spring-boot-test"))
+
 	implementation(project(path: ":spring-boot-project:spring-boot-actuator"))
 	implementation(project(path: ":spring-boot-project:spring-boot-actuator-autoconfigure"))
 	implementation(project(path: ":spring-boot-project:spring-boot-autoconfigure"))
@@ -183,6 +186,10 @@ dependencies {
 	testSlices(project(path: ":spring-boot-project:spring-boot-test-autoconfigure", configuration: "testSliceMetadata"))
 }
 
+dokkatoo {
+	moduleName.set("Spring Boot Kotlin API")
+}
+
 task aggregatedJavadoc(type: Javadoc) {
 	dependsOn dependencyVersions
 	project.rootProject.gradle.projectsEvaluated {
@@ -344,6 +351,9 @@ def antoraApiCatalogContent = tasks.register("antoraApiCatalogContent", Zip) {
 	from(aggregatedJavadoc) {
 		into "java"
 	}
+	from(tasks.named("dokkatooGeneratePublicationHtml")) {
+		into "kotlin"
+	}
 }
 
 def copyAntoraContentDependencies = tasks.register("copyAntoraContentDependencies", Copy) {
@@ -366,6 +376,12 @@ gradle.projectsEvaluated {
 	}
 }
 
+dokkatoo {
+	dokkatooPublications.configureEach {
+		includes.from("src/docs/dokkatoo/dokka-overview.md")
+	}
+}
+
 publishing {
 	publications {
 		getByName("maven") {

spring-boot-project/spring-boot-docs/src/docs/antora/antora.yml

@@ -28,3 +28,5 @@ ext:
     attributes: { external: true}
   - path: [ "Java APIs", "Gradle Plugin" ]
     attributes: { external: true }
+  - path: [ "Kotlin APIs", "Spring Boot" ]
+    attributes: { external: true }

spring-boot-project/spring-boot-docs/src/docs/antora/modules/api/partials/nav-kotlin-api.adoc

@@ -0,0 +1,2 @@
+* Kotlin APIs
+** xref:api:kotlin/index.html[Spring Boot]

spring-boot-project/spring-boot-docs/src/docs/antora/nav.adoc

@@ -6,5 +6,6 @@ include::build-tool-plugin:partial$nav-build-tool-plugin.adoc[]
 include::cli:partial$nav-cli.adoc[]
 include::api:partial$nav-rest-api.adoc[]
 include::api:partial$nav-java-api.adoc[]
+include::api:partial$nav-kotlin-api.adoc[]
 include::specification:partial$nav-specification.adoc[]
 include::appendix:partial$nav-appendix.adoc[]

spring-boot-project/spring-boot-docs/src/docs/dokkatoo/dokka-overview.md

@@ -0,0 +1,2 @@
+# All Modules
+_See also the <a href="../java/index.html" target="_blank">Java API documentation (Javadoc)</a>._