Track failed published messages

[antoniobusrod]

It would be nice to track the exceptions which happen when it is not possible to publish a message, for example, when there is a connectivity problem.

At the moment, there is the post_publish_failure middleware which is called when there is a timeout error (google.cloud.pubsub_v1.exceptions.TimeoutError, but it would not be called for any other error like google.api_core.exceptions.RetryError.

It would be nice to consider the possibility to track these messages through the existing post_publish_failure middleware or new middleware.

[andrewgy8]

Sounds like a great idea @antoniobusrod ! To take some inspiration from others, we can look at the way Dramatiq handles this here