Support appProtocol in canary.service spec

[philnichol]

Describe the feature

I'd like to be able to optionally specify appProtocol in my v1beta1.Canary object.

What problem are you trying to solve?
For Kuma/Kong mesh support, using an annotation to specify the protocol is deprecated and will be removed in a future release.

Proposed solution

I should be able to specify the appProtocol field optionally, but it should default to unset to prevent breaking changes and to support older clusters.

apiVersion: flagger.app/v1beta1
kind: Canary
metadata:
  name: example
spec:
...
  service:
    port: 9898
    targetPort: 9898
    appProtocol: http

I assume it's a case of adding it here and here + tests and docs.

Happy to raise a PR, or alternatively happy for anyone else to do it 😄 .

Thanks in advance for your review, and for maintaining this awesome project!

What do you want to happen? Add any considered drawbacks.

Any alternatives you've considered?

Is there another way to solve this problem that isn't as good a solution?

[stefanprodan]

I’m Ok with adding appProtocol to the canary service spec as an optional field. @philnichol I’m looking forward to your contribution 👍

[philnichol]

Thanks @stefanprodan, have raised a draft with a few questions 😄 #1185