Have exercises expose whether or not they were correct before the deadline

[stijndcl]

I'm currently working on the Dodona Plugin for Visual Studio Code.

One feature we'd like to add, is displaying an icon next to an exercise to show that the user got it right before the deadline (or missed their deadline), as proposed in thepieterdc/dodona-plugin-vscode#57.

Currently, this would require requesting every single submission the user has made to every single exercise in every series, checking which one was the last one before the deadline, and if the user got it right.

This significantly impacts the speed of the plugin (which currently is near-instant), and might as well be held in an attribute in the exercise's respective json file. Dodona itself shows this icon too, so I think the feature could positively impact Dodona as well.

Is it possible to get this implemented? A has_correct_solution field already exists, but a correct_before_deadline field does not.