group membership invitations

- fix display of group information on user and group pages
- send, receive, accept and reject invitations

bookwyrm/templates/user/layout.html

@@ -4,6 +4,7 @@
 {% load utilities %}
 {% load markdown %}
 {% load layout %}
+{% load bookwyrm_group_tags %}
 
 {% block title %}{{ user.display_name }}{% endblock %}
 
@@ -75,7 +76,7 @@
             <a href="{{ url }}">{% trans "Lists" %}</a>
         </li>
         {% endif %}
-        {% if is_self or user.bookwyrm_groups %}
+        {% if is_self or user|has_groups %}
         {% url 'user-groups' user|username as url %}
         <li{% if url in request.path %} class="is-active"{% endif %}>
             <a href="{{ url }}">{% trans "Groups" %}</a>