Batch send PDF donation receipts

[bobintetley]

This is an issue that seems to keep coming back. Some of our US customers want to be able to email PDF receipts for donations and payments for a period.

Originally, I considered a generic mechanism that would work with mail merges, but the chances for incredibly poor performance are extremely high.

This could be added as its own thing, with a new screen under the Financial menu. It allows you to choose a date period to email for, and a multi-select of payment types to include, and a payment document template to use. This way, the normal receipt could be chosen. One email per person should work. The generate donation document code accepts a list of payment IDs, so all the matching ones for the person for the period could be included.

Some kind of limit probably needs to be enforced on this. Maybe use the same limit as mail merge of 1,500 and the same config element.

[bobintetley]

The earlier ticket was #158

[bobintetley]

It might be wise to force the use of reportlab/xhtml2pdf (asm3.utils.html_to_pdf_pisa) to do this for performance reasons, as all the temporary files and spawning processes for wkhtmltopdf will have a high overhead.