Add mattermost
Add mattermost

trevorturk/exception_notification,smartinez87/exception_notification,trevorturk/exception_notification,DennisSchmidt/exception_notification,Aschen/exception_notification,trevorturk/exception_notification,DennisSchmidt/exception_notification,Aschen/exception_notification,Aschen/exception_notification,smartinez87/exception_notification,DennisSchmidt/exception_notification