Consider using UUIDs instead of MessageId

[lionel-faber]

Currently we use routing::MessageId to map responses to their respective responses. With the changes being brought in, can uuid be used instead?

[naturallymitchell]

(aside) nanoid looks better to me than uuid. it's similarly a secure, URL-friendly, unique string ID scheme, which is simpler.

[chpio]

uuid is a well known standard and you can transfer it in binary form in 16 bytes or as an u128