Flatten out underlyingErrors

[bobgodwinx]

Currently

The current implementation of Action doesn't allow you to receive the Swift.Error when .execution is called. But we get an ActionError type which is not really useful because you always have to switch within it to the underlyingError.

Proposal

I think it would be nice for the framework to have something like var underlyingErrors: Observable<Swift.Error> which will only emit when .execution actually has an error

[ashfurrow]

That makes sense to me, I believe ReactiveSwift's Command type has something similar. Let's do it!

[dangthaison91]

Should .errors will be Observable<Swift.Error> while .executionErrors/actionErrors will be Observable<ActionError>? @bobgodwinx

[bobgodwinx]

@dangthaison91 exactly, the idea is to separate the errors related to the output from the executionErrors this will make sure that on .errors we will be getting only Swift.Error. Do plan on submitting a PR?