Migrates `javax` namespaces to their `jakarta` counterparts.

Performs the following notable version bumps:

* Jakarta Servlet API: `4.0.1` -> `6.0.0` (latest)
* JAXB: `2.3.6` -> `4.0.5` (latest)
* Jersey: `2.41` -> `3.1.6` (latest)
* Jetty: `10.0.18` -> `12.0.9` (latest)

The following changes were necessary due to compatibility issues with Jakarta EE 10:

* `io.jsonwebtoken:jjwt`: `0.9.1` -> `0.12.5`
  * Signing and verifying of JWTs with Alpine's `SecretKey` no longer worked. I'm not sure why it worked before, but now the library complained about AES keys not being suitable for HMAC signing. I modified the `JsonWebToken` class to use Alpine's public/private key pair instead, which works. It changes the signature algorithm to `RS512`. I believe this change makes sense anyway.
* The default implementation of `jakarta.json` is Eclipse Parsson. Replaced `org.glassfish:javax-json` with it.
* The default implementation of `jakarta.mail-api` is Eclipse Angus. Added it.

Signed-off-by: nscuro <nscuro@protonmail.com>

…a-ee

Instead of switching to public/private key pair, convert the secret key to the appropriate `HmacSHA*` algorithm instead. Switching the keys used for signing would have been a breaking change.

Signed-off-by: nscuro <nscuro@protonmail.com>