Write a IsFromMailingList matcher

[chibenwa]

James relies on a plugin defined mail processing system. Units of this mail processing system aremailets and matcher.

A matcher represents a condition that an incoming email can satisfy. A mailet represent a treatment of an incoming email (modification of the mail and/or side effect).

We propose, in this issue to implement a IsFromMailingList matcher, in the mailet/standard project.

This matcher will return recipients of the mail if we have good reasons to think the mail is from a mailing list.

You can rely on the AutomaticallySentMailDetector::isMailingList utility.

You will introduce unit tests & class javadoc for your matcher.

See https://issues.apache.org/jira/browse/JAMES-2434