Volunteer contact details should not be separate from user contact details

[russss]

The Volunteer object requires a User, but it has separate email, name, and phone number fields for reasons which are unclear.

This is less then ideal for a few reasons:

• As a user, I don't expect EMF to have multiple different email addresses (or names) for me, particularly on what looks like the same website
• We should not have to duplicate notification code for the volunteer system (c.f. #1052)
• There will likely be other opportunities to share notification methods in future (e.g. push notifications)

For clarity: there is no requirement for the User.name field to be a user's proper/real/"legal" name. Perhaps there's some impression that it should be when people buy tickets, but we could give people the option to change it when they sign up to volunteer.

If anyone has any more insights into why the system is currently designed this way, I'm all ears.

[marksteward]

I'm pretty sure the reason is you can't change your EMF email:

And people might want to be notified on a different email address, or might not even have access to the one that bought them a ticket. Currently we expose this under the volunteering page as an offer to contact people at a different address:

[marksteward]

User.phone is redundant and should be removed at some point.

[russss]

I don't really see why we shouldn't allow people to change their email address to be honest - it's just that we never added that feature (it would certainly be useful on the admin interface as well).