Merge GitOps 'promotion' Pull Requests automatically

[mnuttall]

This issue is part of https://bigblue.aha.io/features/ICPAROAD-326 for those with Aha! access.

The current solution for the "Build and Promote" pipeline builds a microservice and leaves a Pull Request (PR) open, ready to be manually promoted to the GitOps dev repo. This is what's currently going to happen in the pipeline when building from a merge to master of a microservice project:

• Build the microservice project
• Move the updated app-deploy.yaml into the /config directory (creating if needed)
• Create a kustomization.yaml to reference the app-deploy.yaml and any other config files in the /config directory
• Raise a Pull Request against the GitOps repo to check-in the /config directory into /environments/<envName>/services/<project name>/base

This leaves a PR open in GitHub that has to be merged, meaning manual intervention is required to flow changes into the Dev environment.

A working prototype has been developed in https://github.com/rhd-gitops-example/services/tree/master/automerge-example. Use this issue to add automerge support into the appropriate ICPA pipelines as part of Aha-326.

[anneqm]

@kvijai82 @stephenkinder is this one in plan as well?

[anneqm]

This goes with parent epic https://github.ibm.com/IBMCloudPak4Apps/icpa-roadmap/issues/272 and Aha! Link: https://bigblue.aha.io/features/ICPAROAD-326