Bug Fixes
- **type**: Add some type hints in trame_server.core
([`209d212`](https://github.com/Kitware/trame-server/commit/209d21200b840ed92b1302d10718a2369e366fc2))
- **type**: Use Literal for 'backend' and use type alias ClientType
([`bc7375e`](https://github.com/Kitware/trame-server/commit/bc7375e8fb51b1845d297adb3c77498a96b0cec5))
- **type**: Use Literal for 'exec_mode' and remove TypeAlias not available in Python<3.10
([`725d1a7`](https://github.com/Kitware/trame-server/commit/725d1a7c33b94970d5469b642caa152a374bd091))