Document Upgrade Process for NKG

[ja20222]

As a potential user of NKG
I want the NKG project to recommend a path to minimize downtime during upgrades
So that I feel confident that I can use the product in a production environment and not significantly impact traffic during an upgrade.

Acceptance

• Documentation is add here to recommend a upgrade method to minimize downtime for an NKG upgrade.

[mpstefan]

Talked about changing this story to a manual test and documentation for how to ensure limited downtime upgrades.

[mpstefan]

Blocked by #542 and #563