Auto-set email_type to Premium if the email is filtered to premium recipients

[benborgers]

Currently the email_type (which determines who can view an archived email on the web) defaults to Public, even if the email was only sent to Premium subscribers via the new filters.

There's a longer-term solution hiding in here, but for now we should at least detect a Premium email and set the email_type to Premium as well.

https://secure.helpscout.net/conversation/2693726667/5405

[jmduke]

In addition to this, we need to figure out how to deal with checks for:

email.email_type == Email.Type.PRIVATE

[Ben-EvergreenS]

Link to Ticket

Update: user reached out today to show renewals coming through as new premium.