Revert "Merge branch 'fix/accounts-can-belong-to-many-users' into 'master'"

...u/idi/stud/savingsapp/controller/user/UserController.java

...a/no/ntnu/idi/stud/savingsapp/dto/auth/SignUpRequest.java

.../no/ntnu/idi/stud/savingsapp/dto/user/BankAccountDTO.java

...in/java/no/ntnu/idi/stud/savingsapp/dto/user/UserDTO.java

...a/no/ntnu/idi/stud/savingsapp/dto/user/UserUpdateDTO.java

...va/no/ntnu/idi/stud/savingsapp/model/BankAccountType.java

...ain/java/no/ntnu/idi/stud/savingsapp/model/user/User.java

...o/ntnu/idi/stud/savingsapp/repository/UserRepository.java

...java/no/ntnu/idi/stud/savingsapp/service/UserService.java

...tnu/idi/stud/savingsapp/service/impl/UserServiceImpl.java