Migrate to new quarkus-rest

[uw4]

Former resteasy impl in use was replaced in 3.9:

https://github.com/quarkusio/quarkus/wiki/Migration-Guide-3.9#resteasy-reactive-extensions-renamed-to-quarkus-rest-gear-white_check_mark

• Multipart forms needs to be ported
  https://quarkus.io/guides/rest-migration#multipart-support
  https://quarkus.io/guides/rest#multipart

• Usage of jakarta.mail (IMHO this is optional)
  https://quarkus.io/guides/mailer