Validate that service accounts have the right shape

[mattmoor]

In what area(s)?

/area API

What version of Knative?

HEAD

Expected Behavior

Knative should reject a serviceAccountName: foo@bar.baz.

Actual Behavior

I believe we will just let this through to K8s and likely fail creating the deployment (haven't tried, just noticed this in code).

[shashwathi]

/assign @shashwathi

[steren]

Were conformance tests written for this validation?

[shashwathi]

@steren : No. Valid service account is not part of runtime contract(I think) so does it need a conformance test?

[steren]

It's not runtime contract related, but API spec related, I suppose we also test the API?

[shashwathi]

Yes you are right. It is spec related so I will add conformance test for this check 👍
thank you for explaining your thought behind the ask. I appreciate it