Support EU region endpoints #129
Description
SendGrid added a separate API for EU servers.
https://www.twilio.com/en-us/blog/send-emails-in-eu
Support was added to the official sendgrid-python library in 6.10 via a set_sendgrid_data_residency() method sendgrid/sendgrid-python#1073 (although I think this could be done in earlier versions too by setting the host parameter of SendGridAPIClient).
To support this I think we'd need a new optional setting, something like SENDGRID_REGION