Fix mail_room byte_size log field
We have some Sidekiq jobs that process incoming emails. These jobs are special: they are not scheduled by our application directly, but by a third-party component: mail_room.
This means that those jobs don't go through our regular Sidekiq client middleware, and so we lack some visibility. We added https://github.com/tpitale/mail_room/pull/88 upstream to provide structured logging.
However, one of the key fields in this structured logging does not appear to be working: byte_size
. This represents the size of the email that's being stored in Redis.
Fixing this will allow us to re-evaluate #1 (closed) and see what the distribution looks like.