Send compressed payload by gzip

[plazma-prizma]

As shown in the API docs, it is possible to send compressed payload on PutMetricData operation.

In order to do that I need to compress payload before it is being signed and need to add Content-Encoding: gzip.

I can only provide my request_dispatcher to client, and on dispatch phase it receives an already SignedRequest which doesn't help.

Can we add an option to compress payload with gzip without sending it?

I would be happy to implement that.

[matthewkmayer]

This would be good to have!

With #1323 in mind, this should use Cargo flags to only bring in the dependencies and code if the crate user wants the behavior. In other words, if someone does not want to compress the payload, they shouldn't have to download and compile the gzip crate. 😄

[matthewkmayer]

Done in #1615 . Thanks @plazma-prizma ! 🎉