Send various notification emails

[kdmnk]

To users:

• When your registration have been approved
• When admins upload your print balance
• When an other user uploads your print balance
• When you get free pages
• When your roles changed (also this can work as a log)
• When you have to pay the kkt/netreg
• For every transaction paid/received/moved to checkout
• When any of your personal/educational data changed by the secretariat or the admins
• After the status update form deadline, set email to the secretariat about the changes.

To admins:

• When there is a new registration waiting to be approved

To the staff:

• When there is a new fault reported

Feel free to add more

[kdmnk]

Example at #87