Rather than maintain hand coded protocol serialization code, Streams could use the same code-generation framework as Clients/Core.
There isn't a perfect match, since the code generation framework includes an assumption that you're generating "protocol messages", rather than just arbitrary blobs, but I think it's close enough to justify using it, and improving it over time.
Using the code generation allows us to drop a lot of detail-oriented, brittle, and hard-to-maintain serialization logic in favor of a schema spec.
Reviewers: Colin P. McCabe <cmccabe@apache.org>, Boyang Chen <boyang@confluent.io>, Bill Bejeck <bill@confluent.io>, Guozhang Wang <wangguoz@gmail.com>