SSH key is not added, deprecated BasicSSHUserPrivateKey.FileOnMasterPrivateKeySource

[aboutbelka]

Hi, Jenkins SSH Credentials plugin (1.18) removed BasicSSHUserPrivateKey.FileOnMasterPrivateKeySource (https://javadoc.jenkins.io/plugin/ssh-credentials/com/cloudbees/jenkins/plugins/sshcredentials/impl/package-summary.html) so SSH keys can no longer be added from a file by puppet_helper.groovy (line 394), the plugin now stores encrypted key itself.
It was a tricky one to trace as puppet doesn't throw any errors (and neither does jenkins-cli) and was creating an entry in credentials but without any SSH in it.
Is it possible to fix?
Thanks for your time supporting this project :-)