:sparkles: [ENH] Have a self-manager role

We need a role allowing users to manage themself.
What is itself ? If the user username matches a username in a realm it may be the same user but this user surely belongs to only one realm. When we add the right we scope it by realm/userstorage : self-manager-{realm}-{userstorage}
Maybe we want to scope by default an authentication method to a realm but we cannot manage multiple oidc configuration for now so we match all user coming from oidc to a realm while we should be able to configure several realm with oidc self-manager.
With the role added the user should be able to change values like its password but do we want it to be able to change other things like its name ?

Start by tracing how roles, realms, user storages, and authentication methods are represented in the Java service. Clarify whether self-management covers only password changes or also profile fields such as the user's name, and how OIDC users map to realms. Done requires an agreed scope for the self-manager role and support for the intended realm and user-storage combinations.

Written by the indexing model from the issue text.