Rename server_url to server_hostname in registrations

[lzap]

I just noticed that we have a very misleading field name in registrations: server_url. This must not be URL, in fact, it breaks RHSM client it only accepts a hostname or IP:

[server]
hostname = subscription.rhsm.redhat.com

...

[rhsm]
baseurl = https://cdn.redhat.com

Base URL is correct.

I would like to fix this there is still time, tho, @achilleas-k already started using this in his monster CLI integration PR in composer. This draft does not anything yet, I want to discuss this how to approach this.

There are several options:

• Do nothing. :-)
• Keep it as URL and parse the value extracting only the hostname.
• Rename and break the contract.
• Rename but make a fallback unmarshaller that will accept the old field name as well.
• Other ideas.

[mvo5]

AIUI we would have to change "images" here, no? This is just a direct mapping of https://github.com/osbuild/images/blob/423d32a0853f1f7ea6ab03507090a11903792dfe/pkg/customizations/subscription/subscription.go#L11 which is also used in composer. Don't get me wrong, I'm in favor for making this cleaner maybe we could just with alias fields or something so there is less risk of breaking anything?

[lzap]

Yes, that is why I am asking for opinions on how to approach this.

From what I remember, @achilleas-k was always for just "break it, fix it quickly".