Add support for dead-letter topics in streaming subscriptions

[alicejgibbons]

Today there is no way to provide a dead letter topic for streaming subscriptions in either subscribeToEvents() method:

• java-sdk/sdk/src/main/java/io/dapr/client/DaprClientImpl.java

  Line 465 in 9508747

  public <T> Subscription subscribeToEvents(

• java-sdk/sdk/src/main/java/io/dapr/client/DaprClientImpl.java

  Line 483 in 9508747

  public <T> Flux<CloudEvent<T>> subscribeToEvents(String pubsubName, String topic, TypeRef<T> type) {

This is supported in the protos in dapr and should be implemented in the SDK.

[HusseinYasser]

I would like to work on this one

[salaboy]

@HusseinYasser please do .. can you send a PR?

[HusseinYasser]

Will have a look in the next couple of days, and will create a wip pr today