Allow to insert a specific key in ssh settings

[ofirule]

According to docs:

The config.ssh.insert_key setting is either True or False

and the config.ssh.private_key_path is used "If you make your own custom box with a custom SSH key, this should point to that private key"

I would like to be able to insert a specific key from a given path to my VM by using both of this settings together or by using a different key setting