Implement an Email actor which is responsible for sending emails

Issue #65 invalid
Edward Yue Shung Wong
created an issue

We need to make the email functionality reusable. Following the Akka model, this should be an email actor!

TODO: define message interface for Email actor (e.g. EmailMessage object). consider how to handle different types of email.

SEE - TemporaryEmailHelper referenced by MentorNotificationActor