Invoice caching (by caching I mean storing them as a generated PDF)
I would like to request possibility of enabling invoice caching (by caching I mean storing them as a generated PDF files in separate folder which would be divided by year and month). This is needed for situations when client is changing his client details and he want to have access to his older invoices issued for different address or company and I as company owner must have all invoices from time when they where generated. This is also needed if WHMCS owner is changing his company details, invoice design, company logo etc. I know there is already WHMCS addon called "Fixed Invoice Data" but it just stores client information in database and what I'm requesting is keeping whole invoice the way how it was issued.
When invoice is being cached and user is trying to download his invoice then cached invoice should be sent to him instead of generating a new one. Cached invoices should be also available in admin section so admin can also check clients historial invoices instead generating a new one when clicking View PDF.