[Feature] URL parameter form submission

I don't know if I've used the correct term for this, but I'd love to be able to use a URL like:

http://mygreatapp.herokuapp.com/submit?firstname=Bob&secondname=Brown&email=bob@brown.com

that basically skips the form submission page. Main use case that I'm thinking of is a mailing list, where the name and email is already known - this would be amazing.

Perhaps it's already possible, and I've missed it? If not, it doesn't seem like something that would be too hard to add.

The issue names only the form submission page and the /submit URL; start by locating the route or entry point that handles form submissions and how it reads firstname, secondname, and email. Confirm the expected query-parameter behavior and define done as handling the example URL without requiring the form page, with coverage for that URL case.

Written by the indexing model from the issue text.