Allow non-staff users to become admin of course group (bug #603044)

Signed-off-by: Richard Mansfield <richardm@catalyst.net.nz>

htdocs/grouptype/lib.php

@@ -84,6 +84,13 @@ abstract class GroupType {
     public static function can_be_created_by_user() {
         return true;
     }
+    /**
+     * Returns whether a user can be promoted to admin of a group of this
+     * grouptype (by an existing group admin, on the 'change role' page)
+     */
+    public static function can_become_admin($userid) {
+        return true;
+    }
 
     /**
      * Returns the roles this group type implements

htdocs/lib/group.php

@@ -109,10 +109,8 @@ function group_can_change_role($groupid, $userid, $role) {
     // admin role permissions check
     if ($role == 'admin') {
         $group = group_current_group();
-        $user = new User();
-        $user->find_by_id($userid);
         safe_require('grouptype', $group->grouptype);
-        return in_array($group->jointype, call_static_method('GroupType' . $group->grouptype, 'user_allowed_join_types', $user));
+        return call_static_method('GroupType' . $group->grouptype, 'can_become_admin', $userid);
     }
 
     return true;