UI: Support using k8s secrets as git-token and git-username to authenticate to Github when creating tests from UI

[Sonlis]

Is your feature request related to a problem? Please describe.
Currently, if a test source is a git-dir, one can only specify directly a token and username to authenticate to Github when creating a test from the UI.
The CLI supports using secrets sitting in the cluster to authenticate, so the API fields already exists. There's just no way to do it from the UI.

Describe the solution you'd like
Being able to specify whether we want to configure the token from the UI or use already existing secrets in cluster to authenticate with Github.

Describe alternatives you've considered
I considered deploying a Mutating webhook server that would add those fields to the CRD when it's applied cluster-side, but since the API already supports such fields, it is just a matter of adding fields in the UI as well.

Additional context
This would be extremely useful for us as it would enable people who are not tech-oriented to create tests themselves. Also obvious security reasons of not sharing the git token to people.

[Sonlis]

I am currently trying to implement it myself, but it would take a bit of time as I am not so frontend oriented. So if someone beats me to it, please do :D

[vsukhin]

@Sonlis thank you for such a detailed issue!

[TheBrunoLopes]

@fivenp should we perhaps implement this from the test settings page ?

[aabedraba]

@Sonlis is this an ongoing issue for you?

[fivenp]

We wanted to implement this already some time ago – but the UI is currently blocked by this issue: #2842

[Sonlis]

Sorry for the late answer @aabedraba, yes it is still an ongoing issue for us.