✨(backend) add creator field on document and allow filtering on it

We want to be able to limit the documents displayed on a logged-in user's
list view by the documents they created or by the documents that other
users created.

This is different from having the "owner" role on a document because this
can be acquired and even lost. What we want here is to be able to
identify documents by the user who created them so we add a new field.

src/backend/demo/management/commands/create_demo.py

@@ -132,10 +132,13 @@ def create_demo(stdout):
             )
         queue.flush()
 
+    users_ids = list(models.User.objects.values_list("id", flat=True))
+
     with Timeit(stdout, "Creating documents"):
         for _ in range(defaults.NB_OBJECTS["docs"]):
             queue.push(
                 models.Document(
+                    creator_id=random.choice(users_ids),
                     title=fake.sentence(nb_words=4),
                     link_reach=models.LinkReachChoices.AUTHENTICATED
                     if random_true_with_probability(0.5)
@@ -147,7 +150,6 @@ def create_demo(stdout):
 
     with Timeit(stdout, "Creating docs accesses"):
         docs_ids = list(models.Document.objects.values_list("id", flat=True))
-        users_ids = list(models.User.objects.values_list("id", flat=True))
         for doc_id in docs_ids:
             for user_id in random.sample(
                 users_ids,