Investigate sending emails to user when trade is offered/accepted/rejected

[quagliero]

Google Functions via gmail? Ping an API on my DO server and send one that way?

[quagliero]

This looks doable:
https://github.com/firebase/functions-samples/tree/master/quickstarts/email-users
https://github.com/firebase/functions-samples/blob/master/quickstarts/email-users/functions/index.js