[Feature]: Refactoring of ClusterAccess to allow single user cluster access

[christianhuening]

We propose to change how cluster access works in general:

Currently there is an aggregate TenantClusterBinding which grants access, but that is very specific to the Tenant stuff. I would like it better if we could give a single user access to a cluster too. Like a ClusterAccess which can point to a user or a tenant or all users to give all users access to a cluster.

AC:

• Create a new Aggregate called ClusterAccess
• Design this in a way that an admin can
  • give a single user access to a cluster
  • give a tenant access to a cluster
  • give all users access to a cluster (keep in mind that there are roles within a cluster, so there must be a role for this case part of the access too)