Relaunch Existing Pantheon Site Doc Update

[ejcabquina]

Re: Relaunch Existing Pantheon Site

Priority: Medium

Issue Description:

The documentation lacks call outs/reminder for customers that have AGCDN + WAF.

A relaunch that consists of moving the domain from an old site to the newer one requires our Implem team to move relevant AGCDN config.

There should be a bit on this doc page that mentions customers should open a ticket to move the AGCDN+WAF config from the old site to be decommissioned to the new site to relaunched.

Suggested Resolution

If there's an existing documentation to be published about this, let's add or link it in.

If there isn't, let's include a callout/reminder. @stevector