fix: add sender_email to _make_smtp_config test helper

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Co-authored-by: christianlouis <361235+christianlouis@users.noreply.github.com>

backend/tests/unit/test_users_endpoints.py

@@ -52,6 +52,7 @@ def _make_smtp_config(**overrides) -> MagicMock:
         username="user@example.com",
         encrypted_password="encrypted",
         use_tls=True,
+        sender_email="",
         created_at=datetime.now(timezone.utc),
         updated_at=datetime.now(timezone.utc),
     )