## Summary
Add support for IdP identity token authorization for Apple. Apple does
not appear to support access token validation.
This allows a user to pass an identity token directly as a bearer token:
```
curl -H 'Authorization: Bearer Apple-Identity-Token' ...
```
## Related issues
-
[ENG-2000](https://linear.app/pomerium/issue/ENG-2000/core-implement-token-validation-for-apple)
## Checklist
- [x] reference any related issues
- [x] updated unit tests
- [x] add appropriate label (`enhancement`, `bug`, `breaking`,
`dependencies`, `ci`)
- [x] ready for review
