✨(backend) add ancestors links definitions to document abilities

The frontend needs to display inherited link accesses when it displays
possible selection options. We need to return this information to the
client.

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

@@ -74,6 +74,7 @@ def test_api_documents_trashbin_format():
             "accesses_view": True,
             "ai_transform": True,
             "ai_translate": True,
+            "ancestors_links_definitions": {},
             "attachment_upload": True,
             "children_create": True,
             "children_list": True,