Include Kotlin API documentation in the documentation site

Closes gh-40692

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>._