Ability to have app-deploy.yaml per each template

[yharish991]

Is your feature request related to a problem? Please describe.
Currently we are adding a new kafka template in java-spring-boot2 stack. In order to bind the kafka instance to kafka application, we would need to add env vars and do volume mounting, which are not required for the default and kotlin template we have.

Describe the solution you'd like
Ability to have a separate app-deploy.yaml or override the existing one for each template.