Operation_Result constructor Null safety

1. spine_client
2. operations.pb
3. Operation_Result
4. Operation_Result const constructor

Operation_Result enum

1. Constructors
2. Operation_Result
3. Values
4. error
5. response
6. notSet
7. Properties
8. hashCode
9. index
10. runtimeType
11. Methods
12. noSuchMethod
13. toString
14. Operators
15. operator ==
16. Constants
17. values