Feat: FIPS 204

[sebadob]

I wanted to integrate ML-DSA - FIPS 204 in the near future as a first PQC signing option for tokens, and contribute it upstream to the jwt crate Rauthy is using, but the idea has been rejected.

However, Rauthy has support for DPoP tokens already, which this crate does not support, and Rauthy has its own custom implementation for already. To have more flexibility and freedom, the idea is to create a fully custom JWT solution inside Rauthy. This will also make it possible to apply some performance improvements and have cleaner code in the end.