crater Credit/Debit notes

Is your feature request related to a problem? Please describe. In some countries it's mandatory to be able to create a Credit & Debit note and have this stated on the invoice.

E.g. A customer returns one of his ordered products and wants his money back, so you create a credit note stating the amount that will be paid back to the customer.

Explanation (probably better as mine) from the world wide web 😄 :

A credit note is a document issued to record in your accounts that a particular amount was returned to the customer for a paid (or partially paid) invoice. It is also sent to your customer to indicate the cancellation of the payment in the original invoice. ~ https://debitoor.com/dictionary/credit-note

A debit note is for purchases made by your own business.

Explanation (probably better as mine) from the world wide web 😄 :

In other words, a debit note basically acts as a buyer's formal request for a credit note from the seller. The document therefore serves as evidence to support a purchase return in the accounting books of a buyer. ~ https://debitoor.com/dictionary/debit-note

Describe the solution you'd like A separate tab where you can create and manage credit & debit notes or a sub section on the invoices & expenses overview so you can create a new credit & debit note. This should be reflected in the sales & expenses accordingly. It's important that the invoice states that it's a debit or credit note (according to the use case) rather as the word "invoice" on the PDF. It would also be nice if it was possible to reference the credit/debit note to a previously entered invoice or expense.

Describe alternatives you've considered None