spring-projectsGH-3001: add docs

Author: notizklotz

spring-kafka-docs/src/main/antora/modules/ROOT/pages/whats-new.adoc

@@ -67,3 +67,30 @@ See xref:kafka/seek.adoc#seek[Seek API Docs] for more details.
 When this constructor is used, the framework calls the function with the input argument of the current consumer offset position.
 See xref:kafka/seek.adoc#seek[Seek API Docs] for more details.
 
+[[x32-default-clientid-prefix]]
+=== Spring Boot application name as default client ID prefix
+
+For Spring Boot applications which define an application name using the `spring.application.name` property, this name is now used
+as a default prefix for auto-generated client IDs for these client types:
+
+- consumer clients which don't use a consumer group
+- producer clients
+- admin clients
+
+.Example client ids resulting for a Spring Boot application with `spring.application.name=myapp`
+[%autowidth]
+|===
+|Client Type |Before |After
+
+|consumer without consumer group
+|consumer-null-1
+|myapp-consumer-1
+
+|producer
+|producer-1
+|myapp-producer-1
+
+|admin
+|adminclient-1
+|myapp-admin-1
+|===