fix(pgw): add info

Author: RoRoJ

network/public-gateways/reference-content/understanding-v2.mdx

@@ -19,7 +19,9 @@ This document explains what to expect and how to prepare for the upcoming change
 
 ## Summary (TL;DR)
 
-[TODO INSERT BRIEF SUMMARY OF CHANGES AND WHAT USERS MUST DO]
+If you have a [legacy](/network/public-gateways/concepts/#ipam) Public Gateway, or a Public Gateway that is still using the [DHCP object](https://www.scaleway.com/en/developers/api/public-gateway/#path-dhcp-list-dhcp-configurations) or [DHCP entries](https://www.scaleway.com/en/developers/api/public-gateway/#path-dhcp-entries-list-dhcp-entries) from the existing API, you must recreate your Public Gateway in the new v2 API, as these functionalities are being deprecated.
+
+If your Public Gateway is already in [IPAM-mode](/network/public-gateways/concepts/#ipam), and you do not use the DHCP object or DHCP entries (only configurable by the API and not the console) your gateway will be automatically migrated to the new v2, and you do not need to take any action. [TODO - DOWNTIME?]
 
 ## Background: DHCP and IPAM
 
@@ -91,7 +93,9 @@ We will release v2 of the Public Gateway API on [TODO-DATE - SAME DATE?]. During
 
 [TODO - DO USERS WHO DON'T USE LEGACY  / DHCP OBJECT / DHCP ENTRIES HAVE ANY ACTION TO TAKE?]
 
-After a period of [TODO - HOW LONG] weeks/months, v1 of the API will be removed. Any resources that have not been migrated to v2 by this time [TODO - WHAT WILL HAPPEN TO THEM?]
+After a period of [TODO - HOW LONG] weeks/months, v1 of the API will be removed. Any resources that have not been migrated to v2 by this time will cotinue to run, but can no longer be modified, nor recreated on the v1 API if they fail or are deleted. Any CLI, Terraform or other devtool scripts using v1 of the API will no longer function. 
+
+[TODO - IF PGW ON V1 CRASHES, HOW IS IT RECREATED? Elle est remontée à l'identique (y compris basée sur des fonctionnalités dispos uniquement en v1) ? A confirmer.]
 
 ## Further help and support