Description of problem:

Add feature in "katello-certs-check" to check for an unsupported character in the hostname

Version-Release number of selected component (if applicable):
satellite-6.9.

How reproducible:

Steps to Reproduce:
1. add the hostname with an underscore for capsule or satellite
2. Installer will fail
3.

Actual results:

`# capsule-certs-generate [...] --foreman-proxy-cname "sat_cap3.lb.example.com"`

`Parameter foreman-proxy-cname invalid: Elements of the array are invalid: sat_cap3.lb.example.com must match one of (?-mix:\A(([a-zA-Z0-9]|[a-zA-Z0-9][a-zA-Z0-9\-][a-zA-Z0-9])\.)([A-Za-z0-9]|[A-Za-z0-9][A-Za-z0-9\-]*[A-Za-z0-9])\z) during configuration, exiting`

Expected results:

If we can check the SSL certs or the SAN has such hostname, we can warn customers that those hostnames are not supported.

Additional info: