44 Backend Refactor

Changes

Moved database_handler methods to non-static auth class
Moved registration validation to registerValidation class
Made pin generation non-static
Rebuilt register validation to create front-end prompt and check on both front and back end
Changed pb instance creation in hooks.server.js to now use a new instance on each request to stop one instance being used up by multiple people.
Changed isTrainer and isMember to a user.role field of member | trainer | manager