Make SFTP for maven repository use pkey.

[offtherailz]

Description

A variable has been already provided but we need to figure out how to use the pkey (probably we need to create settings.xml contextually to the publish action).

What kind of improvement you want to add? (check one with "x", remove the others)

• Minor changes to existing features
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Build related changes
• CI related changes
• Other... Please describe:

Other useful information