Merge pull request #16 from sam0r040/chore/add_documentation_on_how_to_generate_documentation_at_build_time

Add documentation on how to generate springwolf async api spec at buildtime

Author: stavshamir

docs/faq.md

@@ -48,3 +48,27 @@ Spring Security allows to limit access to authorized users.
 ### How to access the generated documentation within java?
 
 Use the `AsyncApiService` to access the generated documentation.
+
+### How to generate the documentation at build time?
+
+#### With Gradle
+
+You can use the [springdoc-openapi-gradle-plugin](https://github.com/springdoc/springdoc-openapi-gradle-plugin) and configure the plugin
+for springwolf by pointing it to the springwolf docs endpoint: 
+
+```groovy
+openApi {
+    apiDocsUrl = "http://localhost:8080/springwolf/docs"
+    outputDir = file("$buildDir/docs")
+    outputFileName = "async-api.json"
+}
+```
+
+The [springwolf-kafka-example](https://github.com/springwolf/springwolf-core/blob/master/springwolf-examples/springwolf-kafka-example/build.gradle)
+contains a working example.
+
+The plugin will startup the spring boot application by using the `bootRun` task and then try to download the documentation
+from the given `apiDocsUrl` and store it in the `outputDir` and with the given `outputFileName`.
+
+If your application is unable to start up with the bootRun task, see if [customBootRun](https://github.com/springdoc/springdoc-openapi-gradle-plugin#customization)
+properties can help you.