RoundTripEnvelope should use a more compact data format

[muse254]

Problem

If you compare the encoded data for file assets that is sent encoded to JSON, we have a scenario where ~300kb file asset becomes a ~2MB json payload.
A good approach would be to create or use custom binary encoding formats to optimise for size. This would be perfectly backwards compatible with the current API we have in place.
More on this: https://stackoverflow.com/questions/49096721/json-transfer-vs-binary-transfer

[stravid87]

Honestly, I have always imagined that the interceptor would look something like this:

With layers being added / removed as necessary.
"A good approach would be to create or use custom binary encoding formats to optimize for size."
I agree so long as we can find an out of the box solution. For obvious reasons, creating our own -- or even creating an implementation of a well done spec like grpc -- is probably too much.
Instead of encoding, maybe we just consider compression?
https://docs.rs/brotli/latest/brotli/

[muse254]

We added compression in this PR, compression, I should have mentioned that @stravid87.

[muse254]

Let me interest you in one such implementation we can plug and play: https://github.com/bincode-org/bincode

[muse254]

Followup on this issue, we hit an improvement ratio of 0.9998 for a 5MB file asset sample when using bincode compared to JSON bytes.
JSON doesn't seem to be the problem

Leaving the issue open for later investigation.