I noticed, that when converting a quote to an invoice, there is no database field, which references, the quote number in the invoice.
In my invoices I use to also mention the quote.
It would be easy to add a field to the invoice model ip_invoice.quote_ref and insert the quote name in this field during conversion in
Honestly I do not understand you.
When printing the invoice, there is no $quote object available.
So I guess to have the quote_number automatically for printing in the invoice we need to enhance the code - unless there is a functionality I am not aware of, yet.
Addming a field in the pi_invoice table with the originial quote number, which is automatically filled in quote_to_invoicelooks like the best choice to me.
No, there is no $quote object available but some additional, linked data is available directly in the invoice object.
The only thing missing is the join statement in the backend which queries the quotes for one that has the invoice number saved.