Start working on return authorizations service
Build lines from inventory unit (wip)

As the integration also deals with return authorizations it needs to
know how to sync inventory units with Credit Memo lines properly
Create Credit Memo from return authorization
Remote % from return_authorization json

Rack blows when per cent sign is present on message payload
Sync returns with credit memos on return_authorization:new

Still need to handle updated message as well to not create duplicated
returns