Provide email service to Fleet trial instances running on Render via SES

[lukeheath]

Goal

User story
As a Fleet website visitor using a trial Fleet instance running on Render,
I want to be able to receive system emails from my instance
so that I can invite new users to my instance via email and reset my password if I forget it.

For help creating a user story, see "Writing a good user story" in the website handbook.

How?

• As part of the DNS provisioning workflow via Terraform:
  • Create a dedicated SES instance for this Fleet trial instance.
  • Create single IAM user with permission to send emails via the new SES instance.
• Generate an API key for the IAM user and provide to the fleetdm.com web server.
  • Presumably a web hook on fleetdm.com that receives the API key and inserts it into the trial instances DB and updated the render instance. But could be something else if there's a simpler path.

Context

• Kickoff meeting notes