This modification the specification has been changed so that the keychain information is handled by "Credential Plugin", so there is a problem with compatibility with the past version.
But Jenkins official document "Writing Pipeline-Compatible Plugins" say "Instead you should integrate with the Credentials plugin."
I think this mean Information about authentication had better do it handled through "credential plugin" rather than stored by plugin itself.
As there are concerns about compatibility etc. with this change, there is also an opinion that this change is against, so as another method, we have prepared a fix that encrypts and stores the password for compatibility.
Anyway, there is a problem that the password is stored in plain text in the configuration file as it is, so I want to fix this as soon as possible.