Add Shift entity notification methods to MailerInterface.

Signed-off-by: Max Fierke <max@maxfierke.com>
Add application-wide broadcast email setting (for posting to LISTSERV, or similar)

Closes #62

Signed-off-by: Max Fierke <max@maxfierke.com>
Bring NoopMailer up-to-date with MailerInterface

Signed-off-by: Max Fierke <max@maxfierke.com>
Add AppSettingsService dependency to notify_mailer

Signed-off-by: Max Fierke <max@maxfierke.com>
Remove notifyShiftUpdated() from MailerInterface

Signed-off-by: Max Fierke <max@maxfierke.com>
Add shift posted email notifications.

Signed-off-by: Max Fierke <max@maxfierke.com>
Add 'Shift Picked Up' and 'Shift Denied' email notifications.

Closes #56.

Signed-off-by: Max Fierke <max@maxfierke.com>