👔(backend) doc restricted by default

By default a created document was in "authenticated"
mode, we switch to "restricted" by default.

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

@@ -47,6 +47,7 @@ def test_api_documents_create_authenticated_success():
     assert response.status_code == 201
     document = Document.objects.get()
     assert document.title == "my document"
+    assert document.link_reach == "restricted"
     assert document.accesses.filter(role="owner", user=user).exists()