feat(UserInfoFetcher): Add XFSC AAS backend

[fhennig]

Description

To integrade with gaia-x we need to fetch user claims from the AAS. this can be done with the UserInfoFetcher.

part of: https://github.com/stackabletech/marispace-x/issues/55

The integration test contains a small python container that mocks the API.

contains CRD changes, new backend: aas

        clusterConfig:
          userInfo:
            backend:
              aas:
                hostname: aas.$NAMESPACE.svc.cluster.local
                port: 5000

Definition of Done Checklist

• Not all of these items are applicable to all PRs, the author should update this template to only leave the boxes in that are relevant
• Please make sure all these things are done and tick the boxes

# Author
- [x] Changes are OpenShift compatible: Add serviceaccounts to test containers
- [x] CRD changes approved
- [x] CRD documentation for all fields, following the [style guide](https://docs.stackable.tech/home/nightly/contributor/docs-style-guide).
- [x] Helm chart can be installed and deployed operator works
- [x] Integration tests passed (for non trivial changes)
- [x] Changes need to be "offline" compatible

# Reviewer
- [x] Code contains useful comments
- [x] Code contains useful logging statements
- [x] (Integration-)Test cases added
- [x] Documentation added or updated. Follows the [style guide](https://docs.stackable.tech/home/nightly/contributor/docs-style-guide).
- [x] Changelog updated
- [x] Cargo.toml only contains references to git tags (not specific commits or branches)

# Acceptance
- [ ] Feature Tracker has been updated
- [ ] Proper release label has been added

[fhennig]

ci test: https://ci.stackable.tech/view/02%20Operator%20Tests%20(custom)/job/opa-operator-it-custom/86/ 🟢

[NickLarsenNZ]

Nice one. Left some comments, but pretty much non-blockers.

[nightkr]

Haven't reviewed the tests

[fhennig]

@nightkr @NickLarsenNZ I still need to fix the test and run it again, but I think code wise everything should be fine. i didn't want to click "Resolve" on the open things, I wanted to leave it to you.

Edit: new test run 🟢

[nightkr]

Still not a complete review

[nightkr]

Largely LGTM. Did not run the tests myself. Ticked docs since I agree with not documenting this while it's experimental.