✨(backend) allow filtering by documents marked as favorite

We recently allowed authenticated users to mark a document as favorite.
We were lacking the possibility for users to see only the documents
they marked as favorite.

src/backend/core/tests/documents/test_api_documents_list.py

@@ -433,7 +433,6 @@ def test_api_documents_list_filter_is_creator_me_invalid():
     results = response.json()["results"]
     assert len(results) == 5
 
-
 # Filters: is_favorite
 
 
@@ -496,7 +495,6 @@ def test_api_documents_list_filter_is_favorite_invalid():
     results = response.json()["results"]
     assert len(results) == 5
 
-
 # Filters: link_reach