Feature: Update User role should fail fast for unknown user IDs

[arvindh123]

Is your feature request related to a problem? Please describe.

During update user role for non existence user id, doesn't fails in policy layer, Instead it fails in repo layer after adding policy in spiceDB them it rollback the policy.

Describe the feature you are requesting, as well as the possible use case(s) for it.

Instead of checking the user existence in repo layer, we should check user id is belongs to Magistrala Platform as member in policy layer( spiceDB).

Indicate the importance of this feature to you.

Should-have

Anything else?

No response