Prevent overwriting data on import form outside data source

bookwyrm/activitypub/base_activity.py

@@ -107,7 +107,9 @@ class ActivityObject:
             setattr(self, field.name, value)
 
     # pylint: disable=too-many-locals,too-many-branches
-    def to_model(self, model=None, instance=None, allow_create=True, save=True):
+    def to_model(
+        self, model=None, instance=None, allow_create=True, save=True, overwrite=True
+    ):
         """convert from an activity to a model instance"""
         model = model or get_model_from_type(self.type)
 
@@ -129,9 +131,12 @@ class ActivityObject:
 
         # keep track of what we've changed
         update_fields = []
+        # sets field on the model using the activity value
         for field in instance.simple_fields:
             try:
-                changed = field.set_field_from_activity(instance, self)
+                changed = field.set_field_from_activity(
+                    instance, self, overwrite=overwrite
+                )
                 if changed:
                     update_fields.append(field.name)
             except AttributeError as e:
@@ -140,7 +145,9 @@ class ActivityObject:
         # image fields have to be set after other fields because they can save
         # too early and jank up users
         for field in instance.image_fields:
-            changed = field.set_field_from_activity(instance, self, save=save)
+            changed = field.set_field_from_activity(
+                instance, self, save=save, overwrite=overwrite
+            )
             if changed:
                 update_fields.append(field.name)