Ferreteria/v0.5/stash

Ferreteria 0.5: message stashing

About

Sometimes a process emits output right before a redirect needs to happen -- most commonly in response to a form submission (we do a redirect right after processing POST input in order to prevent accidental data resubmissions).

For this reason, the redirect system checks for output (which would/should not yet have been sent to the screen anyway), stashes it via the stash cookie, and then does the redirect. The page object should always look for any stashed content to display, adding it at the top of any content it adds to the render. (This last part is currently not working, 2022-12-03.)