refactor removing user from group

This is in preparation for removing a user and their lists when the group owner blocks them.
Remove the user via models.group
Remove the lists via models.list

bookwyrm/models/group.py

@@ -85,6 +85,15 @@ class GroupMember(models.Model):
             group=join_request.group,
         )
 
+    @classmethod
+    def remove(cls, owner, user):
+        """remove a user from a group"""
+
+        memberships = cls.objects.filter(group__user=owner, user=user).all()
+        for m in memberships:
+            # remove this user
+            m.delete()
+
 
 class GroupMemberInvitation(models.Model):
     """adding a user to a group requires manual confirmation"""

bookwyrm/models/list.py

@@ -2,6 +2,7 @@
 from django.apps import apps
 from django.db import models
 from django.db.models import Q
+from django.db.models.fields import NullBooleanField
 from django.utils import timezone
 
 from bookwyrm import activitypub
@@ -87,7 +88,24 @@ class List(OrderedCollectionMixin, BookWyrmModel):
     def direct_filter(cls, queryset, viewer):
         """Override filter for "direct" privacy level to allow group members to see the existence of group lists"""
 
-        return queryset.exclude(~Q(group__memberships__user=viewer), privacy="direct")
+        return queryset.exclude(
+          ~Q( # user not self and not in the group if this is a group list
+              Q(user=viewer) | Q(group__memberships__user=viewer)
+          ), 
+          privacy="direct"
+        )
+
+    @classmethod
+    def remove_from_group(cls, owner, user):
+        """remove a list from a group"""
+
+        memberships = GroupMember.objects.filter(group__user=owner, user=user).all()
+        for m in memberships:
+            # remove this user's group-curated lists from the group
+            cls.objects.filter(group=m.group, user=m.user).update(
+                group=None, curation="closed"
+            )
+
 
 class ListItem(CollectionItemMixin, BookWyrmModel):
     """ok"""

bookwyrm/views/group.py

@@ -163,6 +163,10 @@ def remove_member(request):
     if not user:
         return HttpResponseBadRequest()
 
+    # you can't be removed from your own group
+    if request.POST["user"]== group.user:
+        return HttpResponseBadRequest()
+
     is_member = models.GroupMember.objects.filter(group=group, user=user).exists()
     is_invited = models.GroupMemberInvitation.objects.filter(
         group=group, user=user
@@ -182,13 +186,8 @@ def remove_member(request):
     if is_member:
 
         try:
-            membership = models.GroupMember.objects.get(group=group, user=user)
-            membership.delete()
-
-            # remove this user's group-curated lists from the group
-            models.List.objects.filter(group=group, user=user).update(
-                group=None, curation="closed"
-            )
+            models.List.remove_from_group(group.user, user)
+            models.GroupMember.remove(group.user, user)
 
         except IntegrityError:
             pass