epics and saga middleware

[beyondeye]

In my effort to improve support for rx and provide better middleware for async action, I should implement
epics and saga.
For epics see for reference https://redux-observable.js.org/docs/basics/Epics.html
There is also an implementation in kotlin for rxjava by Michael Pardo here: https://github.com/pardom/redux-observable-kotlin
A very similar middleware that is independent from rx is redux-saga
http://yelouafi.github.io/redux-saga/
I could implement both, merging interfaces, for having the same functionality both when using rxjava or something else (kotlin coroutines/ kovenant promises)