+'AuthChangeFormFields': After converting a field information array obtained
+from a set of AuthenticationRequest classes into a form descriptor; hooks
+can tweak the array to change how login etc. forms should look.
+$requests: array of AuthenticationRequests the fields are created from
+$fieldInfo: field information array (union of all AuthenticationRequest::getFieldInfo() responses).
+&$formDescriptor: HTMLForm descriptor. The special key 'weight' can be set
+ to change the order of the fields.
+$action: one of the AuthManager::ACTION_* constants.
+