Changes to List admin-managed model provider credentials

added the optional property items/proxy_url to the response with the 200 status

added the new internal_error enum value to the type response property for the response status 401

added the new internal_error enum value to the type response property for the response status 503

added the new permission_error enum value to the type response property for the response status 401

added the new permission_error enum value to the type response property for the response status 503

added the optional property items/session_sticky_keys to the response with the 200 status

endpoint added