Email notifications to setter when assigned a route and for new comments on routes

[skeltont]

The owner of a route should receive an email when:

• a maintenance request is filled for their route
• a route is assigned to them
• their route receives a comment

[jonahgeorge]

Email content?
If the route is re-assigned (if we can do that), should an email be sent to the new owner?
This is mainly a notification for the owner of route, correct? Since an admin will be assigning users

copied from dupe

[jonahgeorge]

Let's use an after_save callback:

• On create, send email to owner
• On update, compare new owner to previous owner value, if changed send email to owner

[jonahgeorge]

Do we care about spamming users with emails? Should we add a virtual boolean property on routes called notify_owner? If false, this callback isn't triggered.