Check SFTP Service: Extend with SSH-key Authentication

As more and more companies only offer SFTP connection via PPK Authentication it would make sense to extend the "Check SFTP Service" with an option to connect via an SSH Key (e.g. Private key is on the checkmk server). It would do the same as the current Check SFTP Service but with the possibiity to use Public-Private-Key-Authentication. Otherwise companies are forced to allow only for monitoing password authentication for their sftp-server. This is very critical in many industries