Define operator upgrade procedure requirements

[pmalek]

Problem statement

We should define clear upgrade requirements so that both developers and users are aware what's to be expected when one upgrades the operator from 1 version to another.

For instance:

• Whether users should expect particular resources to be recreated/updated
• Whether users should expect operator managed Pods to be restarted/recreated

These and more should be codified in documentation and ideally a test harness #155 should be introduced to enforce those.

Acceptance criteria

• As a User I have clear expectations on what will happen when I upgrade the operator from version X to version Y

[lahabana]

@pmalek to link to related issue