software/rapid-cdn: avoid RegExp to validate hostnames

Using RegExp to validate hostnames is a bad practice, and has a lot of reasons to be wrong.
On top of that, the JSON Schema specification allows, since draft 7, to validate hostnames
against an IDN hostname, by using the `idn-hostname` format.

With these changes, IDN are now supported (.рф and .中國 for instance), and long TLD
should not be a problem anymore.
9 jobs for erp5-zope2-tests
Status Job ID Name Coverage
  External
passed ERP5.StandaloneDeploymentScriptTest-Debian.Buster

00:30:01

passed SlapOS-Master.StandaloneDeploymentScriptTest-Debian.Buster

00:36:23

passed Wendelin.StandaloneDeploymentScriptTest-Debian.Buster

00:20:05

failed Wendelin.StandaloneDeploymentScriptTest-Debian.Buster.Master

15:02:07

passed ERP5.StandaloneDeploymentScriptTest-Debian.Buster

08:55:05

passed SlapOS-Master.StandaloneDeploymentScriptTest-Debian.Buster

00:37:07

passed Wendelin.StandaloneDeploymentScriptTest-Debian.Buster

00:35:06

failed Wendelin.StandaloneDeploymentScriptTest-Debian.Buster.Master

failed Wendelin.StandaloneDeploymentScriptTest-Debian.Buster.Master

15:02:06