refs https://github.com/TryGhost/Team/issues/2253
refs https://github.com/TryGhost/Team/issues/2254
This package is analogous to the @tryghost/member-events package. The
events here will be consumed by the EmailSuppressionList
implementation and used to add emails to said list. They'll be
dispatched by the code which handles events received from Mailgun.
