Handle `Host` without a tlsSecret.name defined in a better way

[alexbowers]

Please describe your use case / problem. Currently, when you want to create a Host for a new Hostname (eg. something.example.com) you can define a Host. If you want to have TLS with this as well, you would define a Certificate (via Cert Manager).

If you're using HTTP-01 challenge on the certificate, then you need the Host to be accessible.

To do that, with a Mapping you would define a Mapping as shown in the documentation; however, there is a problem.

There isn't a Host thats registered, because the certificate secret is invalid (or doesn't exist).

To counter this, you need to have a wildcard Host (hostname: '*').

It would be better if the Host instead "downgraded" itself to one without the TLS configuration, so that it was ready to receive HTTP requests to handle the Cert Manager request.

[alexbowers]

This is especially a problem if you're registering many Hostnames (such as providing a service where you can register a custom domain)