Package maillist sends bulk e-mail to lists of addresses using
the Sendgrid API.
All functionality is implemented as methods on a session object,
which should be closed when finished with it.
The script 'init-db.sh' should be run to initialize the database for this
Open a new session.
Create or retrieve an Account.
Create or retrive a List (which contains subscribers).
Optionally add more subscribers to the list.
Create and schedule a campaign for that list.
This package will ensure the emails are sent out when the scheduled
time is reached as long as at least one session remains open.
Example session of sending a single test email. Configuration here is read
from the environment.