Messaging page alert updates for non-Cerner patients

[ambikaroos]

User Story When a Veteran who is not a patient at a Cerner facility is logged in on VA.gov and is on the Messaging page (https://www.va.gov/health-care/secure-messaging/), the alert box should explain to users that they will be directed to the appropriate page on MHV. [This is the status quo, but design pattern may need to change to reflect changes being made for Cerner patients]

Acceptance Criteria

• [ ] Alert box UX lets authenticated users know that they will be directed to MHV, and provides correct link to MHV messaging page
• [ ] TBD: New tab automatically opens with correct MHV messaging page (current behavior)
• [ ] Unauthenticated experience of the alert box is unchanged

[bridgethapner]

Based on conversations so far, I don't believe the Alerts UX or content will change for non-Cerner patients, only other content on the page. That could change & we can keep these tickets as open & ready just in case.