Feat/models: Implement Models

[Diegogagan2587]

Implemented Changes

• Set up models according to the ERD Diagram.
  • create User model with next properties
    • name
    • has many Groups
    • has many Entity
    • Include validations test
  • Create Entity model with next properties
    • AuthorId
    • Name
    • Amount
    • CreatedAt
    • belongs to User
    • belongs to Group
    • Include Validation tests
  • Group: include next properties
    • Name
    • Icon
    • Created at
    • belongs to User
    • has many Entities
    • Include validation test