AuthCode constructor Null safety

1. conduit_core
2. conduit
3. AuthCode
4. AuthCode constructor

AuthCode class

1. Constructors
2. AuthCode
3. Properties
4. clientID
5. code
6. expirationDate
7. hasBeenExchanged
8. hashCode
9. isExpired
10. issueDate
11. requestedScopes
12. resourceOwnerIdentifier
13. runtimeType
14. Methods
15. noSuchMethod
16. toString
17. Operators
18. operator ==