Cacheable constructor Null safety

1. sendbird_sdk
2. cache_service
3. Cacheable
4. Cacheable constructor

Cacheable class

1. Constructors
2. Cacheable
3. Properties
4. dirty
5. hashCode
6. key
7. primaryKey
8. runtimeType
9. Methods
10. copyWith
11. noSuchMethod
12. toString
13. Operators
14. operator ==