Implement v2 MCP Controller

[Diaphteiros]

Understand the Task

Description
In v1, the user creates a single ManagedControlPlane resource which is then split up into multiple service components. This approach doesn't work with the extension concept of v2. Still, the idea is that a user first creates an ManagedControlPlane resource and then multiple service resources next to it.

We need a controller for the v2 variant of ManagedControlPlane, with the following properties:

• The MCP resource contains authentication and authorization information (compare: Authentication and Authorization resources in v1).
• The controller creates a ClusterRequest for the MCP and uses AccessRequests to ensure the configured authentication and authorization.
• It must take care to not delete the corresponding Cluster before all services are gone, since we might otherwise leak resources.
• The controller should be part of the openmcp-operator.

Any further valuable resources.

No response

What is required to accept the Task as done.

Done Criteria

• Implement MCP controller.
• Write unit tests.
• Merge reviewed code into main.
• Present in review.

[Diaphteiros]

We had a longer discussion today on how we can make sure that the ManagedControlPlane resource is not deleted before all its services have been deleted. The problem here is that the MCP controller does not know which service resources exist and therefore cannot check if any are left. The service providers itself could watch the MCP to notice it being deleted, but this would require a somewhat specific logic in each service provider, and we want to keep them simple, since we expect open-source contributors to add further service providers.

We discussed this solution:

• The ServiceProvider resource gets a list of resource types (apiGroup, version, kind) in its status, with each entry corresponding to one service resource it provides.
• Each service provider that reconciles one of its service resources adds a finalizer to the corresponding MCP resource. The finalizer has the format services.openmcp.cloud/<name> with <name> being the .metadata.name of the ServiceProvider resource.
• When an MCP is deleted, the MCP controller checks for finalizers with the services.openmcp.cloud/ prefix. For each that it finds, it fetches the corresponding ServiceProvider from the platform cluster, takes its list of service resources from the status and searches for these resources (with the same name and namespace as the MCP itself). It triggers the deletion of each resource found this way.
• The service providers remove their finalizer on the MCP again after their service resources have been successfully deleted.

[Diaphteiros]

Main controller implementation is done. Currently working on unit tests. I expect to find some bugs which need fixing.