What is this mule-app-maven-plugin is used for ? https://docs.mulesoft.com/release-notes/mule-app-maven-plugin/mule-app-maven-plugin-release-notes
and also i see maven-clean-plugin ?if we use mvn clean in the command isnt it sufficient do we need to add this plugin in the pom.xml
It is a legacy Maven plugin used to build Mule 3.x applications. In Mule 4 it has been replaced by the newer Mule Maven Plugin: https://docs.mulesoft.com/mule-runtime/4.3/mmp-concept