Set up automatic email notifications

[sarahlazarich]

Based on the outcome of Morgan's design doc, set up automatic updates. There are currently ~2800 users that have signed up for notifications. We should make sure that these users are ported over to the new tool and will receive notifications.

Design Template: https://www.figma.com/file/0Rj4I74uO1UTBkHzDR25UD/Automated-Email-Templates?type=design&node-id=1607-68638&mode=design&t=wv7FKcX2qxWmCIpM-0

AC:

• When a new listing is posted in doorway, an email automatically goes out to the listserv of people that signed up for notifications
• The notification email follows the template made by design
• Users can unsubscribe from emails if needed
• BAHFA can manage their own listserv and emails

Technical details if using Sendgrid:

• Create proper configuration in SendGrid
  • Create a sender in the SendGrid UI. This step needs a bit more research on what the best plan of attack is since the sender has to be a valid email on an authenticated domain. We could potentially use the email created for partners
• Update code to accommodate this new use case.
  • Add new Handlebar template
  • When listing is published programmatically create a single send via this api. https://docs.sendgrid.com/api-reference/single-sends/create-single-send
  • The campaign will not send until you schedule the send. This can be done via the schedule single send api https://docs.sendgrid.com/api-reference/single-sends/schedule-single-send. We can set it to send “now”

Notes:

• We should put this behind a feature flag in the backend

[ludtkemorgan]

This has been moved to the Doorway repo with appropriate subtasks