Merge branch 'f-get-username' into 'dev'

ENH: convenience function for getting the username from a connection object

See merge request !5

src/caosdb/connection/connection.py

@@ -611,3 +611,12 @@ class _Connection(object):  # pylint: disable=useless-object-inheritance
         _handle_response_status(http_response)
 
         return http_response
+
+    def get_username(self):
+        """
+        Return the username of the current connection.
+        
+        Shortcut for: get_connection()._authenticator._credentials_provider.username
+        """
+        return self._authenticator._credentials_provider.username
+