Create a cloud method to create environment variables at the job level

[jallen13]

Currently there is only a method to create environment variables at the project/environment level, but we need a way to create environment variables at the job level using these definitions: https://documenter.getpostman.com/view/14183654/UVsSNiXC#15529393-6fa2-419d-89dc-ca083d4c276e