CRUD operations on the IAM setting Restrict User Domains should be available via API/CLI

We automate provisioning of all IBM Cloud accounts. IAM settings for "Restrict API Key Creation" and "Restrict Service ID Creation" are available with API, CLI and terraform. But, "Restrict User Domains" https://cloud.ibm.com/iam/settings can only be changed manually in the UI. This is an important setting for us, and should be available for automation, so this isn't one step we need to do manually and also it's less error prone (we don't want to accidentally restrict the wrong domain due to a typo...)