Use form for saving list items

bookwyrm/models/list.py

@@ -2,6 +2,7 @@
 import uuid
 
 from django.apps import apps
+from django.core.exceptions import PermissionDenied
 from django.db import models
 from django.db.models import Q
 from django.utils import timezone
@@ -74,6 +75,22 @@ class List(OrderedCollectionMixin, BookWyrmModel):
             return
         super().raise_not_editable(viewer)
 
+    def raise_not_submittable(self, viewer):
+        """can the user submit a book to the list?"""
+        # if you can't view the list you can't submit to it
+        self.raise_visible_to_user(viewer)
+
+        # all good if you're the owner or the list is open
+        if self.user == viewer or self.curation in ["open", "curated"]:
+            return
+        if self.curation == "group":
+            is_group_member = GroupMember.objects.filter(
+                group=self.group, user=viewer
+            ).exists()
+            if is_group_member:
+                return
+        raise PermissionDenied()
+
     @classmethod
     def followers_filter(cls, queryset, viewer):
         """Override filter for "followers" privacy level to allow non-following