Notification constructor Null safety

1. wings_data_model
2. wings_data_model
3. Notification
4. Notification constructor

Notification class

1. Constructors
2. Notification
3. Properties
4. category
5. dateTime
6. hashCode
7. id
8. name
9. read
10. runtimeType
11. Methods
12. noSuchMethod
13. rebuild
14. toBuilder
15. toString
16. Operators
17. operator ==