Ensure the Amazon SES mailer is ready to use

Ensure the Amazon SES mailer is ready to use

Fix https://gitlab.com/gitlab-org/gitter/webapp/-/issues/2573

Testing strategy

1. In the @gitterhq/env project, run npm link
2. In the webapp project, run npm link @gitterhq/env
3. Get the amazonses__accessKeyId and amazonses__secretAccessKey secrets and put them in your webapp .env
4. In the webapp project, run node .\scripts\utils\send-unread-notification-email.js --username MadLittleMods --room-uri MadLittleMods/postcss-css-variables --dummy

Todo

• Add CI variables
  • mandrill__apiKey
  • amazonses__accessKeyId
  • amazonses__secretAccessKey
• Update lib/mailers/legacy_mandrill_templates with the latest from Mandrill (specifically unread emails)