[Auth] Implement User entity using Typeorm

[ahmedeid6842]

Requirements:

At this task the user entity "user schema" should be implemented using typeorm

Done:

• Create user entity.
• Added user columns id, userName, email and password.

  follow this ERD for the datatypes and constraints

• Take advantage of Typeorm Generators to set the constraints and validation.
• Added the created entity to Postgres entities.