Add harvest email functional test

[rshewitt]

User Story

In order to have confidence harvest emailing works correctly, datagov wants to add a functional test verifying the SMTP service is sending the email to the configured recipient(s).

Acceptance Criteria

[ACs should be clearly demoable/verifiable whenever possible. Try specifying them using BDD.]

• GIVEN a harvest email to send
  WHEN the email is sent
  THEN the recipient receives the email.

Background

[Any helpful contextual notes or links to artifacts/evidence, if needed]

Security Considerations (required)

[Any security concerns that might be implicated in the change. "None" is OK, just be explicit here!]

Sketch

[Notes or a checklist reflecting our understanding of the selected approach]