[ECOM-423] Add `SoapOrderHeaderService`
This PR adds the SoapOrderHeaderService using the new WSDL provided by @lloyd-carter.
Please review: @ahoffmann @weizhong-wang @lloyd-carter
GitLab (git.doit.wisc.edu) has been upgraded to version 18.2.8. For more, see: https://about.gitlab.com/releases/2025/07/17/gitlab-18-2-released/
This PR adds the SoapOrderHeaderService using the new WSDL provided by @lloyd-carter.
Please review: @ahoffmann @weizhong-wang @lloyd-carter