TAG constant Null safety

1. baguette
2. MessengerKey
3. MessengerKey
4. TAG constant

MessengerKey class

1. Constructors
2. MessengerKey
3. Properties
4. hashCode
5. runtimeType
6. Methods
7. noSuchMethod
8. toString
9. Operators
10. operator ==
11. Constants
12. TAG
13. UPDATE_CONVERSATIONS
14. UPDATE_MESSAGES