Allow adding password for private key in ClientSSLCertConfig.FromClientCertFile

[csar]

Is your feature request related to a problem? Please describe.
Quite often the file under keyPath requires a password to load, for those I need to decode this first and put it into a tempFile

Describe the solution you'd like
Add an Option[Secret] to FromClientCertFile

Describe alternatives you've considered
Another constructor FromClientCertString that contains the PEMs directly, this will be useful if such resources are received from somewhere else

Additional context
N/A