Add API to pre-populate fields

[cdman]

The use-case would be to pre-populate an invoice but still allow the user update/edit the information before generating/sending the final invoice. Something like:

If you go to https://invoice-generator.com/?from=foo&to=bar then the "From" and "To" fields should be pre-populated with "foo" and "bar" respectively.

[jaredk2g]

This is an interesting request. Do you mind sharing more about why you want to do this?

[cdman]

@jaredtking - I would like to provide a button to my colleagues to create an invoice for a set of orders from our clients. However sometimes clients ask for customizations and I want to give my colleagues the option to edit the different fields before creating the PDF and sending it to the client.

I imagine in 99% of the cases they will just click the "Download Invoice" link, but for the 1% of the cases it would be great to be able to edit some fields before generating the invoice.