Kong Identity: EGW + terminate + plain how to

## Jobs to be done (optional)

## Definition of done
- how to for EGW + terminate + plain (API required)

## Information
PRD: https://docs.google.com/document/d/17-1_Z-MqRrafqJj2yFRdoHJD020DfjJO2IAnkppqWGw/edit?tab=t.0#heading=h.t2sb3fotc3tr

## Due date (optional)

June 8

## Size
L

Start with the linked PRD to determine the intended Kong Identity documentation scope and the meaning of EGW, terminate, and plain. Produce a how-to covering those three cases with the required API, and verify that the published guide satisfies the definition of done.

Written by the indexing model from the issue text.