Stabilization 1.14 (2)

What's Changed

• CO-3824 : adding the new note from the statement to the invoice created by @TheRaphael0000 in #1428
• CO-3835 : Make "Write a letter" page available without login by @TheRaphael0000 in #1434
• Co3807 - Generate test cases fails by @duvenhage in #1435
• CO-3830 : change of email trigger a merge of mass.mailing.contact by @TheRaphael0000 in #1430
• CO-3832 : add constrain on invoice validation by @TheRaphael0000 in #1431
• Cs592 - Tipps zum Schreiben grammer mistakes by @duvenhage in #1419
• CO-3840 : Cannot generate payment slips for sponsorship in december if next_invoice_date is for next year by @TheRaphael0000 in #1436
• Stabilization 1.14 (2) by @ecino in #1438

Full Changelog: v12.0.1.15...v12.0.1.16