Simplify UserDetailsService, fix UserRepository to use JpaRepository or MongoRepository with the correct ID type.
(so no need to declare a separate save method, as it is already provided by Jpa and Mongo Repository)
Migrated to Spring Websocket

Fix #844
Merge pull request #916 from gzsombor/userrepo-fix

Simplify UserDetailsService, fix UserRepository to use JpaRepository or ...
Cleaned up the old files to remove, as we upgrade a major version