Add plan command node-token command

[alexellis]

Add plan command node-token command

Description

• k3sup plan is used to read in a list of devices and to generate an installation script for a HA cluster.
• k3sup node-token is used by scripts generated by k3sup plan to avoid too many SSH connections by each joining node back to the server.
• SSH connection code is moved into a common helper method, instead of getting repeated

How Has This Been Tested?

Usage:

devices.json

[{
        "hostname": "node-1",
        "ip": "192.168.1.128"
}]

Command:

k3sup plan \
  --tls-san $SAN \
  --servers=3 \
  --user ubuntu \
  --background=true/false > bootstrap.sh

chmod +x bootstrap.sh

./bootstrap.sh

See testing below:

https://www.youtube.com/watch?v=o4UxRw-Cc8c&feature=youtu.be

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

Additional notes required in README..

Future plans:

• Additional flags from k3sup install/join should be added to k3sup plan
• --yaml flag to be added as an option for human-generated inputs to k3sup plan