[Feat] Add JWT support

[ndrean]

In the NATS-client, it is just an extra field jwt, and a matter of not sending the publicKey recalculated because it is already contained in the JWT.

For testing, everything is in the CI workflow.
It uses nsc

• setup an Oeprator
• setup an Account
• and use the MEMORY resolver
• Then you can create a user dynamically signed by this Account, get the credentials (JWT and seed)
• and execute the tests using the JWT and SEED (to sign the nonce sent by the server, who will read the publicKey from the JWT to verify thee JWT, so no need to pass the recomputed publicKey from the seed)

So it is mostly nats-server config.

[ndrean]

ah, I forgot to remove my working files.