Makes attachment Images a serializable class

bookwyrm/models/attachment.py

@@ -0,0 +1,31 @@
+''' media that is posted in the app '''
+from django.db import models
+
+from bookwyrm import activitypub
+from .base_model import ActivitypubMixin
+from .base_model import ActivityMapping, BookWyrmModel
+
+
+class Attachment(ActivitypubMixin, BookWyrmModel):
+    ''' an image (or, in the future, video etc) associated with a status '''
+    status = models.ForeignKey(
+        'Status',
+        on_delete=models.CASCADE,
+        related_name='attachments'
+    )
+    class Meta:
+        ''' one day we'll have other types of attachments besides images '''
+        abstract = True
+
+    activity_mappings = [
+        ActivityMapping('id', 'remote_id'),
+        ActivityMapping('url', 'image'),
+        ActivityMapping('name', 'caption'),
+    ]
+
+class Image(Attachment):
+    ''' an image attachment '''
+    image = models.ImageField(upload_to='status/', null=True, blank=True)
+    caption = models.TextField(null=True, blank=True)
+
+    activity_serializer = activitypub.Image