id property Null safety

1. next_photo
2. features
3. User
4. id property

User class

1. Constructors
2. User
3. Properties
4. address
5. company
6. copyWith
7. email
8. hashCode
9. id
10. name
11. phone
12. runtimeType
13. username
14. websiteUrl
15. Methods
16. noSuchMethod
17. toString
18. Operators
19. operator ==