Handle some events before servant takes over

[ikervagyok]

Is it be possible, to pass in a function that resolves high-level application-specific effects into lower level effects like State x and especially into Error ServerError? This function would just be a chain of event-handlers.
This way you can use only high level effects in all servant handlers. You can resolve high level effects that could result in a Error ServerError before the servant machinery kicks in and all other effects still propagate outside.

servant-effectful/src/Effectful/Servant.hs

Lines 95 to 100 in 1e574e6

	interpretServer :: Env es -> Eff (Error ServerError : es) a -> Servant.Handler a
	interpretServer env action = do
	v <- liftIO $ do
	es' <- cloneEnv env
	unEff (runErrorNoCallStack action) es'
	T.liftEither v

(I know its possible to handle effects in each effect handler manually, but that seems a lot more tedious than to have a clear boundary between the effects that could cause an Error ServerError and generic ones that can't/shouldn't.)

[ikervagyok]

After taking another stab at it, I think hoistServer might be enough for most cases which are in the form of Eff es a -> Eff es' a. only effects like Error aren't supported to my understanding, which would be Eff es a -> Eff es' (Either (Callstack, error) a)
If that level of support is enough for this library, maybe some documentation is enough