Jwthenticator

Fixed timezone offset when verifying JWT tokens

Fixes:
* If a path to a non-existing RSA keys is configured, a set of keys will be created in this path

Fixes:
- `/jwks` is fixed and now works as expected (and is also tested properly)

Features:
- Added support for receiving a list of comma separated JWT audiences (instead of only a single one), single audience is still supported
- `kid` (key id) is now included in the created JWT headers

Tweaks:
- Changed consts to be imported from env variables using the `environs` package
- Small documentation improvements
- Expanded `PyJWT` requirement to allow v2.0+
- Capped `SQLAlchemy` version to v1.4.0 due to breaking changes on that release

- Added support for JWT payload audience
- Added JWT algorithm parameter to `Client` class to supress `pyjwt` warning

* Expanded cryptography's supported versions to include v2.8

- Improved dependencies support for easier integration into ongoing projects