$user: user to promote.
&$promote: groups that will be added.
-'GetBlockedStatus': after loading blocking status of an user from the database
+'GetBlockedStatus': DEPRECATED since 1.34 - use GetUserBlock instead. After
+loading blocking status of a user from the database
&$user: user (object) being checked
'GetCacheVaryCookies': Get cookies that should vary cache options.