Set the password callback for the TLS private key file.
@param config The neo4j client configuration to update.
@param callback The callback to be invoked whenever a password for
the certificate file is required.
@param userdata User data that will be supplied to the callback.
@return 0 on success, or -1 on error (errno will be set).
Set the password callback for the TLS private key file.
@param config The neo4j client configuration to update. @param callback The callback to be invoked whenever a password for the certificate file is required. @param userdata User data that will be supplied to the callback. @return 0 on success, or -1 on error (errno will be set).