Expose available IDPs in MCP status

[ValentinGerlach]

What would you like to be added:

The list of effective IDPs (system IDP + custom IDPs) should be available in the MCP's status field. We are already exposing this information in the kubeconfig secret (referenced by .status.components.authentication.access) but it is hard for the UI to parse this information.

Suggested format:

apiVersion: core.openmcp.cloud/v1alpha1
kind: ManagedControlPlane
metadata:
  name: test-mcp
  namespace: project-test
spec:
  ...
status:
  components:
    authentication:
      access:
        ...
      identityProviders:
        - name: openmcp
          issuer: https://openmcp.example.com
          clientId: 171187c6-5560-45a4-a135-e21c8b18a7ac
          scopes:
            - email
            - profile
            - offline_access
          pkce: auto
          interactive: true
        - name: gh-actions
          issuer: https://token.actions.githubusercontent.com
          clientId: https://github.com/octo-org
          interactive: false

Why is this needed:

The UI could use this information to show a list of available IDPs and start an OIDC login flow for the IDP by the user.

openmcp-project/backlog#172 (comment)

[andreaskienle]

Just an idea: Consider renaming ⁠showInUI to ⁠isInteractive or something similar, i.e. what the IdP actually does rather than just where it shows up. That way the dependencies would flow from the UI to the resource definition (the UI just looks for IdPs with this flag) instead of the resource having to know about UI stuff.

[ValentinGerlach]

Good point, thanks!