Kong Identity: Migrate from consumers/consumer groups to principals (fast follow)

## Jobs to be done (optional)

## Definition of done
- How to that explains how to migrate from consumers/consumer groups to principals (will need draft)
- works for OIDC, key auth, basic auth, but pick key auth for the guide (process will be the same)
1. Create principals
2. Link consumer to principal
3. Adjust plugin to auth against principal instead of consumer (this step can differ), to minimize downtime, clone plugin (3.15), change config of one to hit consumer, one to hit principal so that if one doesn't work the other one will.

## Information
DRP: Andrew J.
PRD: https://docs.google.com/document/d/17-1_Z-MqRrafqJj2yFRdoHJD020DfjJO2IAnkppqWGw/edit?tab=t.8y6auuawn7n8

## Due date (optional)

after June 8 release

## Size
L