Evaluating switching to Capsule ProxySetting rather than using RoleBindingReflector

[prometherion]

Starting the discussion from #266 (comment) thanks to @MaxFedotov:

I remember why I added this feature. The idea was the following:

• Tenant admin create a role and rolebinding in one of his namespaces for user Bob. This role has a limited set of permissions (it is not cluster-admin)
• Bob must be able to see all namespaces, where he has access when running kubectl get ns

This reflector caches all rolebindings and is used for getting a list of namespaces to be shown for each of the users.
And as reflectors are asynchronous by default, this can add a delay between kubectl create ns and kubectl get ns

Now capsule-proxy adds new ProxySetting CRD, which can be used to add permissions for both, tenant admins and normal users. But removing this reflector would require tenant admins to create a separate ProxySetting CRD for each of the users rolebindings in all namespaces.

My thoughts: we could create a specific addon that replicates the ProxySetting resources for each ServiceAccounts that has GET permission on its Namespace, in order to let them list Namespace as would happen for a regular user.

Not sure if this would be the duty of capsule-proxy here, but I'd like to get feedback from end-users and adopters.

[MaxFedotov]

From one side I like the idea of moving to ProxySetting, as it can be seen as a natural capsule way.

But on the other side, I don't like the idea of breaking the current design (and being not backward-incompatible), which can be already used by the community (and yes, it is already used by us :) ) and will require them to perform additional activities during and update and afterward.