API Ruby on Rails

I need somebody who can implement an API for our Ruby and Rails application with this application:

https://downloads.abacus.ch/fileadmin/ablage/abaconnect/htmlfiles/cmdline/AbaConnect_Handbuch_en.pdf

API calles "lohn" - see api examples: https://downloads.abacus.ch/en/downloads/abaconnect/webservices