Account login via email link/revolving password

When a PDF invoice is mailed, a dynamic link in the email would allow client to immediately access the invoice and pay it without login/password. Then they could pay an invoice using an non-db driven "unsaved" method (such as redirection to paypal or other account-based payment module that doesn't used stored info in blesta).

Of course, using a stored cc, account actions, ordering services, would all require a login using username/password.

Alternatively, the user id could be auto-filled via email link, as well as auto-generated passcodes that are invoice specific that could be listed in the email, for login for payment of the invoice.

This way, just simply accessing a link via email would bring up the invoice to easily/quickly pay the amount due without the client needing to know another account name/password.