SpiceDB is an open source, Google Zanzibar-inspired, database system for creating and managing security-critical application permissions.

SpiceDB

caveat:
```
caveat within_allowed_days(current_date datetime, until datetime) {
  current_date <= until
}

definition datasource {
  relation has_access: usergroup#member with within_allowed_days
}
```

or use expiration (better option): https://authzed.com/docs/spicedb/concepts/expiring-relationships

```
definition datasource {
  relation has_access = usergroup#member with expiration
}
```