Formatter for converting model images to AP Images

Replaces reduntant properties on user and book models

bookwyrm/models/book.py

@@ -12,6 +12,7 @@ from bookwyrm.utils.fields import ArrayField
 
 from .base_model import ActivityMapping, BookWyrmModel
 from .base_model import ActivitypubMixin, OrderedCollectionPageMixin
+from .base_model import image_attachments_formatter
 
 class Book(ActivitypubMixin, BookWyrmModel):
     ''' a generic book, which can mean either an edition or a work '''
@@ -60,15 +61,6 @@ class Book(ActivitypubMixin, BookWyrmModel):
         ''' the activitypub serialization should be a list of author ids '''
         return [a.remote_id for a in self.authors.all()]
 
-    @property
-    def ap_cover(self):
-        ''' an image attachment '''
-        if not self.cover or not hasattr(self.cover, 'url'):
-            return []
-        return [activitypub.Image(
-            url='https://%s%s' % (DOMAIN, self.cover.url),
-        )]
-
     @property
     def ap_parent_work(self):
         ''' reference the work via local id not remote '''
@@ -106,7 +98,10 @@ class Book(ActivitypubMixin, BookWyrmModel):
 
         ActivityMapping('lccn', 'lccn'),
         ActivityMapping('editions', 'editions_path'),
-        ActivityMapping('attachment', 'ap_cover'),
+        ActivityMapping(
+            'attachment', 'cover',
+            image_attachments_formatter
+        ),
     ]
 
     def save(self, *args, **kwargs):