<form class="ajax" id="changeUserGroupForm" action="server_privileges.php" method="post">
    {{ Url_getHiddenInputs(params) }}
    <fieldset id="fieldset_user_group_selection">
        <legend>{% trans 'User group' %}</legend>
        {% trans 'User group' %}:
        {{ Util_getDropdown('userGroup', all_user_groups, user_group, 'userGroup_select') }}
        <input type="hidden" name="changeUserGroup" value="1">
    </fieldset>
</form>