<!-- This is an auto-generated comment: release notes by coderabbit.ai
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## Summary by CodeRabbit
* **New Features**
* Introduced user access tokens, enabling users to generate, list, and
revoke personal access tokens via the GraphQL API.
* Added GraphQL mutations and queries for managing access tokens,
including token creation (with optional expiration), listing, and
revocation.
* Implemented authentication support for private API endpoints using
access tokens in addition to session cookies.
* **Bug Fixes**
* None.
* **Tests**
* Added comprehensive tests for access token creation, listing,
revocation, expiration handling, and authentication using tokens.
* **Chores**
* Updated backend models, schema, and database migrations to support
access token functionality.
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