Allow user to provide their own certificates to system sites, using just secrets

[fgiorgetti]

Is your feature request related to a problem? Please describe. The existing mechanism that allows users to provide their own custom certificates when dealing with system sites, is through placing the actual certificates into specific directories before starting the respective system namespace.

Describe the solution you'd like The existing mechanism can be easily improved to allow users to provide theiro own certificates by simply placing secrets under input/resources.

This is a nice enhancement, especially, when combined with the new system apply CLI command, as users could easily provide their own secrets, without the need to deal with directories and files.

And this is not just a benefit for the CLI users, but to people using the skupper.v2 Ansible collection, as it also allows Secrets to be provided through the skupper.v2.resource module.