Externally Sourced Configuration Files Values

I would like to use - - configExpand command-line option both for - - rest and - - exec expansion for specific configuration file option only not for complete or entire configuration file option. Since , I do not have adequate infrastructure / platform like my own domain name and also correspoinding ssl certificates , I am unable to proceed further. Just for testing purposes , is there any site where I can test it with their domain name and their correspoinding ssl certificates ?