AuthCredentialsAdapter constructor Null safety

1. irte_engine
2. credentials.adapter
3. AuthCredentialsAdapter
4. AuthCredentialsAdapter constructor

AuthCredentialsAdapter class

1. Constructors
2. AuthCredentialsAdapter
3. Properties
4. endpoint
5. hashCode
6. runtimeType
7. Methods
8. authenticate
9. noSuchMethod
10. post
11. toString
12. Operators
13. operator ==