Hide matomo users who have access to a site but not made by AlternC

Users made in the Matomo interface and given an access to a site
that's in AlternC show up without this restriction. When that happens,
the user is no longer able to modify permissions for any of the Matomo
users from their AlternC account.

bureau/class/m_piwik.php

@@ -165,6 +165,12 @@ class m_piwik {
                     $api_data->$user = 'noaccess';
                 }
             }
+            # Hide users who have access, but are not in AlternC
+            foreach (get_object_vars($api_data) as $user => $access) {
+                if (!in_array($user, $this->alternc_users)) {
+                    unset($api_data->$user);
+                }
+            }
             return $api_data;
         }
         else return FALSE;