develop implementation plan for tracking email sends to patients

[mirrorstage]

Description

In Metabase, we currently track Text Message Sent and Text Message Status in their respective tables. We do not, however, track email sent in support of the patient results-available notification.

As a Call to Action (CTA), an email is an important moment in the user journey where the application has nearly completed its value exchange with the user in the overall test/result loop. We also pay to send these. For both reasons, it would be useful to have our own count of emails sent. TBD if "status" is equally useful, as I/@mirrorstage don't know enough about that table's operations or intended use.

Proposed solution

Start tracking email sends, storing the data in Metabase.

Additional context

I believe we also send "Welcome to SimpleReport" emails to admins at new organizations. This could be an interesting secondary use case but needs review.

[DanielSass]

At first glance, it looks like similar to our sms tooling - sendgrid has webhooks that could theoretically give use similar updates: https://www.twilio.com/docs/sendgrid/for-developers/tracking-events/event

Should try to verify if there are billing implications for this feature.

[mirrorstage]

@DanielSass came here to ask "why do you suppose we track SMS in the first place but not SendGrid?" and discovered the answer is: Alicia wanted it -- #1266 -- in April 2021. but then maybe had forgotten about it by July when SendGrid was applied to this use case -- #2027