Add upgrade path to Domain config

I've tried your patch @JeroenT but it fails to apply it.

Coming in a few years after the fact, but wanted to share how our project did it simply. We had a project that used this module. It was seemingly straight forward to "hand migrate" the configuration settings to Domain Config, using the Domain Config UI. We had about 6 domains for reference. If anyone else is looking for an upgrade path, I might recommend that.

• Copy and paste the Domain Site Settings configuration from domain_site_settings.domainconfigsettings.yml into a notes application for reference
• Uninstall Domain Site Settings module
• Install the Domain Config UI module (Domain Config was already installed)
• Go to /admin/config/system/site-information
• Select the domain that you want to configure
• Go back to your configuration settings that you pasted into your notes
• Fill out the requisite values for the site name, front page, 404 page etc
• Save!
• Repeat those configuration steps in the Site Information page for each domain until you are done.
• That should be it from what I can tell.

There are a few other steps about removing the module from composer that are part of the normal Drupal workflow, but wanted to share how we upgraded from this module to Domain Config without a need for automation.

The patch is indeed not working. But you actually just need this install file that does the work. I'll provide a new patch file so users can actually use it.

There you go. Hiding the patch file as its not applying.