RxJava2 bridge doesn't forward all events

[margelatu]

When using the RxJava2 client, the AsyncHandler implementation provided by the client code is wrapped in a bridge, see https://github.com/AsyncHttpClient/async-http-client/blob/master/extras/rxjava2/src/main/java/org/asynchttpclient/extras/rxjava2/DefaultRxHttpClient.java#L71

The bridge is an instance of MaybeAsyncHandlerBridge or of ProgressAsyncMaybeEmitterBridge. Irrespective of which of the two classes the bridge instance belong to, most of the events that are part of the AsyncHandler interface are not forwarded to the underlying AsyncHandler implementation. This includes events like onRequestSend or onRetry, making it impossible for users of the RxClient to handle them without rewriting the whole client.

The problem is in AbstractMaybeAsyncHandlerBridge, which does not forward these events.

[margelatu]

Opened PR #1636 to address this issue.

@slandelle : could you please review this? Thank you!

[slandelle]

Thanks!