Yet another small fix

app/models.py

@@ -542,7 +542,8 @@ class User(HashidMixin, UserMixin, db.Model):
     )
     followed_corpora = association_proxy(
         'corpus_follower_associations',
-        'corpus'
+        'corpus',
+        creator=lambda c: CorpusFollowerAssociation(corpus=c)
     )
     jobs = db.relationship(
         'Job',
@@ -1499,7 +1500,8 @@ class Corpus(HashidMixin, db.Model):
     )
     followers = association_proxy(
         'corpus_follower_associations',
-        'follower'
+        'follower',
+        creator=lambda u: CorpusFollowerAssociation(follower=u)
     )
     user = db.relationship('User', back_populates='corpora')
     # "static" attributes