Divide cache wrappers to api and implementation

[zTrap]

[sksamuel]

What's the context for this change ?

[zTrap]

Actually it is the best practice for all public shared code 🙂 Dividing makes able to use kotlin's interface delegation e.g

class SharedCache<K, V>(impl: CacheWrapper<K, V>) : CacheWrapper<K, V> by impl, AnotherInterface

[zTrap]

Also after this changes both wrappers will be acceptable for wildcards. Since they implements single parent interface CacheWrapper<K, V>

[sksamuel]

I'm not really a fan of interfaces where they are not needed. You can easily test code using the caeffine builder, since it's in memory, so the "mock" use case isn't needed. What else is having an interface buying us?