Add new attributes to user model and create new entity to link with user

[codingleo]

Currently the user model has only 3 attributes. It would be good to have a few more attributes a one more entity with one-to-many relationship for a better view about how graphql works with multiple entities.

User:

• firstName
• lastName
• birthDate
• email
• password
• userType

Post:

• userId
• title
• intro
• body
• comments

Comment

• userId
• postId
• body