[Feat] Implement POST /users/sign-up

[JonghunYu]

Is your feature request related to a problem? Please describe.

• We need to add new endpoint for user sign-up
• We have to store the password as a hash string so we can't revert back to plain password but we can still verify the password

Describe the solution you'd like

• Implement new POST /users/sign-up endpoint and remove existing POST /users endpoint
• Input / output parameters would be as below, the jwt token can be generated by UserService

IN/OUT	Field	Type	Description
IN	email	string	email address
IN	password	string	user's password
OUT	message	string	response message
OUT	token	string	JWT token

• the password stored in DB must be hash string generated by sha256 algorithm

Additional context

• Make sure to write unit test as well as e2e test