fix(iam): add info on migration (#5213)

Author: ldecarvalho-doc

pages/iam/how-to/manage-members.mdx

@@ -41,6 +41,7 @@ Watch our interactive demo for a visual guide on how to manage IAM Members on th
 
     <Message type="important">
       If you did not send a welcome email to the Member, make sure you give them their login information.
+      The following link allows them to see the log in screen only for your Organization: `https://account.scaleway.com/member-login?organization=[orgid]`. You must replace `[orgid]` with your Organization ID.
     </Message>
 
 ## How to access the Member overview

pages/iam/reference-content/guests-to-members-migration.mdx

@@ -88,3 +88,7 @@ You receive an email to confirm the migration. The former Guests, now Members, a
 <Message type="important">
   If you are a Member in more than one Organization with the same email address, you can switch between Organizations. You must perform a first connection as a Member to remain connected and easily switch between Organizations. A first login is required for each device you use to connect to the Scaleway console. You remain logged into each device unless you clear your cookies.
 </Message>
+
+## Automatic member migration
+
+From the 15th to the 17th of July 2025, all Guests in all Scaleway Organizations will automatically become Members. During the migration, all Guests will be logged out of the Organizations and will have to [log back in as Members](/iam/how-to/log-in-as-a-member).