SMHHeadRequest<T> constructor Null safety

1. smh_flutter_sdk
2. smh_user_requests
3. SMHHeadRequest<T>
4. SMHHeadRequest constructor

SMHHeadRequest class

1. Constructors
2. SMHHeadRequest
3. Properties
4. hashCode
5. runtimeType
6. Methods
7. method
8. noSuchMethod
9. path
10. request
11. serviceKey
12. toString
13. URLMethod
14. Operators
15. operator ==