Move injectors to ManagedCredentialType

[chrismeyersfsu]

Injectors are a bail-out mechanism for when you need to do something that the templating engine does not support, for a particular credential type. They are strongly tied to one and only one credential type. Before this change they lived far away from the ManagedCredentialType they are associated for. The link was the credential kind string was the same as the injector function name. This was a very loose coupling. This change is a tighter coupling.

[AlanCoding]

Putting this in my own words...

The custom logic like awx_plugins.credentials.injectors.aws already lived here, but there was no link in the plugin definition to the custom logic. So somehow that got referenced by a literal name like "aws".

My only gripe would be that post_injectors doesn't feel like a great name. Like, sure, maybe it runs after the other stuff (templates)? But it's usually an alternative to the templates, making that detail kind of irrelevant practically. It's more important that it runs custom python logic like a caveman, as opposed to any structured injector definition.

[chrismeyersfsu]

1. injectors_override
2. custom_injectors
3. alt_injectors
4. injectors_fn

[AlanCoding]

I'd lean towards (2) myself.

[webknjaz]

I had an alternative idea with ansible/awx_plugins.interfaces#10 / #50 / ansible/awx#15595 FTR

[AlanCoding]

I slightly lean towards the sentiment @chrismeyersfsu expressed in ansible/awx#15595

So I lean more towards getting rid of this "problem" by bringing these custom injectors closer to the ManagedCredentialType they are related to.

But even if we did nothing, it wouldn't bother me that much, since they already live in the plugins repo.

[webknjaz]

@chrismeyersfsu typing change handling instructions:

1. Merge Adopt the custom_injectors callback awx_plugins.interfaces#13
2. Click Run workflow @ https://github.com/ansible/awx_plugins.interfaces/actions/workflows/ci-cd.yml, entering 0.0.1a2 precisely in the version field. Don't enter anything else and submit the form.
3. Wait until the newly created workflow run completes tests and pauses, then approve releasing on the workflow run summary page.
4. Wait until the workflow run completes fully.
5. Click Run workflow @ https://github.com/ansible/awx-plugins/actions/workflows/pip-tools.yml, entering awx_plugins.interfaces in the only input field.
6. Wait until that workflow completes and opens a PR with the version bump in the lock files.
7. Go to that PR and undraft it. You can approve it and enable auto-merge at this point.
8. Once that PR is merged, you can rebase this one.