Add backend for user management and favorite

[Lim Chee Kin]

• sign up - user registration
  • Spring Boot JWT https://www.youtube.com/playlist?list=PLeFUpOmPweSggaTrntYcExlf0JSA20Pu-
• login/logout
  • https://www.filledstacks.com/post/building-flutter-login-and-sign-up-forms/
  • https://github.com/jzahmatkesh/LoginUI (https://www.youtube.com/watch?v=LS8KFYsR244)
• forgot password (email temp password)
• change password
• user profile
  • https://youtu.be/81XYs6lliB4
  • https://github.com/JohannesMilke/user_profile_example
  • https://github.com/JohannesMilke/user_profile_ii_example
• favorite/unfavorite showcase
• social login
  • https://www.callicoder.com/spring-boot-security-oauth2-social-login-part-1/
  • https://github.com/callicoder/spring-boot-react-oauth2-social-login-demo
• cache
  • https://www.baeldung.com/hibernate-second-level-cache