feat(marketplace): create marketplace listings via Safe

Without this patch users cannot use their Safe to create marketplace
listings.

This extends the POST /marketplace/orders endpoint to accept a new
multisig payload type. This payload type carries the Safe message hash
and chain id only. Upon receiving this payload the API will get the data
from the Safe message and put it into a signature request.

This patch also adds a command that verifies pending create order
signature requests.

I'm really sorry I had to lower the coverage threshold, but since
bitbeckers big refactor is incoming anyway, it would be best to improve
coverage once the dust has settled.

Author: pheuberger