Access control

[DoooMer]

An example:
Generate temporary code (invite), use this code before start filling persons. When code is expired - show alert and reset progress.

Add request form. User print email and send form.
Requests save into database.
In order by queue, with some delay, requests are processing - generate unique access code and send him to email.

User go back to the site and enter your access code. Access code activate in this moment for limited time (several minutes).
User do work and when process is end (emails was sent to recepients) - access code to be disabled.

[DoooMer]

Using embeded DB. Expiration of access skipped.