Custom emails sent upon status change

(Updated issue title)

Instead of dramatically complicating the user interface for creating signup-enabled nodes, when changing user(s) signup status, the user should be presented with a form that contains a default email message to be sent at that moment. This will allow users to customize the message for each status change.

I'm porting the signup_status_mailer module to D6 and giving it a major re-write. There are going to be settings for each status on the site, both site-wide and per-node overrides. I'll be committing directly to CVS, but stay tuned for screenshots and questions about UI issues and such.

Since there are a few different ways a signup status can change, I don't think it's viable to always present a form for a custom message to send with a specific status change... I think we just need the flexibility of all these message templates and let sites configure things as needed.

FYI: these are both committed now, which will help here:
#549646: Expose signup-related node and signup values to token.module
#549648: Expose signup_status values to token.module

Subscribing.

Initial D6 version committed to HEAD: http://drupal.org/cvs?commit=252340

I'll post some follow-up issues for a few lingering TODO items that can be handled separately.

FYI:

#551862: singup_status_mailer settings UI cleanup
#551864: Add admin notification emails for signup_status_mailer

Automatically closed -- issue fixed for 2 weeks with no activity.