IApiConfig constructor Null safety

1. cloudinary_url_gen
2. api_config
3. IApiConfig
4. IApiConfig constructor

IApiConfig class

1. Constructors
2. IApiConfig
3. Properties
4. callbackUrl
5. chunkSize
6. hashCode
7. runtimeType
8. timeout
9. uploadPrefix
10. Methods
11. noSuchMethod
12. toString
13. Operators
14. operator ==