Added template tag to get all unjoined groups

tavern/templatetags/tavern_unjoined_filters.py

@@ -0,0 +1,11 @@
+from django import template
+
+from tavern.models import get_unjoined_groups
+
+register = template.Library()
+
+
+@register.assignment_tag
+def get_user_tavern_unjoined_groups(user):
+    user_unjoined_groups = get_unjoined_groups(user)
+    return user_unjoined_groups