Add VA Notify webhook to action needed emails

[steele-lm]

Issue Description

VA Notify is adding a web hook to vets-api that will allow teams to track the success or failure of specific email templates. Once available, we need to monitor success/failure for all our "action needed" emails.

Additional work will be done in other tickets to retry the "action needed" email using the address listed in the Veteran's profile (if different).

---

Tasks

• [ ] Add failure email success/failure monitoring to:
  • COE
  • PCPG
  • VRE

Acceptance Criteria

• [ ] We know when an "action needed" email fails to reach the Veteran

[steele-lm]

Blocked: Waiting for the webhook to be implemented by VA Notify.