deprecated property Null safety

1. conduit_open_api
2. open_api_v2
3. APIOperation
4. deprecated property

APIOperation class

1. Constructors
2. APIOperation
3. Properties
4. castMap
5. consumes
6. deprecated
7. description
8. extensions
9. hashCode
10. id
11. parameters
12. produces
13. referenceURI
14. responses
15. runtimeType
16. schemes
17. security
18. summary
19. tags
20. Methods
21. decode
22. encode
23. noSuchMethod
24. toString
25. Operators
26. operator ==