98887 Callback implementation for IVC emails - IVC CHAMPVA forms

[michaelclement]

Summary

This PR adds a custom callback class for use with IVC emails sent through VA Notify. The main purpose of the callback is to improve our Data Dog displays of emails being sent so we can monitor successful/failed deliveries and how many emails are sent per form.

This PR is part of an ongoing effort. To fully test this callback, the callback class needs to be merged into staging. I've added a feature flag so this can be safely tested without impacting production.

Related issue(s)

• Callback implementation to monitor confirmation emails sent by VA Notify va.gov-team#98887

Testing done

• New code is covered by unit tests
• Prior to this callback, there was not an IVC specific log trail for confirmation emails being sent
• To verify the new monitor method works as intended, the code changes may be pasted into the staging argo terminal and the monitor class instantiated + track_email_sent invoked. However, to verify the VA Notify integration the code has to be fully merged into staging so that whichever node receives the VA Notify callback will have the latest code.

Screenshots

NA

What areas of the site does it impact?

IVC CHAMPVA forms

Acceptance criteria

• I fixed|updated|added unit tests and integration tests for each feature (if applicable).
• No error nor warning in the console.
• Events are being sent to the appropriate logging solution
• Documentation has been updated (link to documentation)
• No sensitive information (i.e. PII/credentials/internal URLs/etc.) is captured in logging, hardcoded, or specs
• Feature/bug has a monitor built into Datadog (if applicable)
• If app impacted requires authentication, did you login to a local build and verify all authenticated routes work as expected
• I added a screenshot of the developed feature

Requested Feedback

NA

[stevenjcumming]

@michaelclement there's a failing test