Modify client_registration_types_supported in TA's metadata_policy for OP

[marche271]

Together with @abisegna and @fmarino-ipzs, we have reviewed the operations related to the client_registration_types_supported parameter in a Trust Anchor's (TA) metadata_policy for an OpenID Provider (OP), for interoperability with OpenID Federation.
Currently, it requires the supported value to be automatic with the subset_of operation. However, in Federation, it could be either automatic or explicit.
Therefore, the proposal is to have:

• subset_of: automatic, explicit
• superset_of: automatic

This change ensures better compatibility with OpenID Federation.