Created factory for participant for test purposes.
Implemented emails and leads methods in Crew class. Covered by specs.
Added factory for crew lead.
Implemented participants mailer created action (covered by specs).
Designed email for crew lead sent by register the new participant.
Implemented integration tests for 'register new participant' feature.
Designed email erb templates for participants related notifications.
Implemented all actions of participants mailer.
Created the set of custom email RSpec matchers.
Made mailers specs and mailer classes more DRY.
Implemented sending emails by register the new participant.
Make all specs passed.
Implemented the set of email related matchers.