Code review comment for lp://staging/~florian-angermeier/contractor/filter-functions-based-on-file-size

Well, for now, we can let them here. For instance, for the icon one, while it is strictly speaking optional, we do want to force developers to put an icon. Whereas for the max file size, it does not make sense for a lot of contracts (print for instance), so it is really an optional field (and not an optional-if-one-really-is-too-lazy-to-write-it one).