Get the user metadata of the user used to sign the request
Currently it is not possible to get the metadata of a user without specifying the user ID via /admin/metadata/user=xyz. In some cases it is necessary to retrieve the metadata of the user that is used to sign the API request. To to so i suggest to implement something like /admin/metadata/user?self.
In the Dashboard it is necessary to check if a RGW user that is going to be deleted is not the user account that is used to access the RGW Admin OPS API. The problem is that the Dashboard only knows about the access/secret key of the administration account. With the above feature it is easy to retrieve the user name of the administration account.