broker error handler support and interface changes (#501)

* broker: update to micro broker changes

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

options.go

@@ -1,25 +0,0 @@
-package nats
-
-import (
-	"github.com/micro/go-micro/v2/broker"
-	nats "github.com/nats-io/nats.go"
-)
-
-type optionsKey struct{}
-type drainConnectionKey struct{}
-type drainSubscriptionKey struct{}
-
-// Options accepts nats.Options
-func Options(opts nats.Options) broker.Option {
-	return setBrokerOption(optionsKey{}, opts)
-}
-
-// DrainConnection will drain subscription on close
-func DrainConnection() broker.Option {
-	return setBrokerOption(drainConnectionKey{}, true)
-}
-
-// DrainSubscription will drain pending messages when unsubscribe
-func DrainSubscription() broker.SubscribeOption {
-	return setSubscribeOption(drainSubscriptionKey{}, true)
-}