save

<div class="container">
        <form>
            <div class="form-group">
                <label for="sel1">Select the group to which you want to add users</label>
                <select class="form-control" id="sel1">
                    <#list groups! as group>
                        <option value="${group.id}" name="id">${group.groupName}</option>
                    </#list>
                </select>
            </div>
            <div class="form-group">
                <label for="sel2">Select user</label>
                <select class="form-control" id="sel2">
                    <#list users! as user>
                        <option value="${user.id}" name="id">${user.username}</option>
                    </#list>
                </select>
            </div>
            <div class="form-group">
                <button type="submit" class="btn btn-primary">Добавить</button>
            </div>
        </form>
    </div>