Correct a suggestion

Rewrite a battle that was already suggested. The author may correct their own whatever became of it, a turned-down one included: a rejection carries the moderator's reason, and the answer to it is usually a correction rather than a second submission. A moderator may correct anyone's while holding the signed link the moderation channel hands out. The body is the submission's, so the same checks apply: the map and mode are validated against the catalogue, a random battle names its vehicle, and the one-row-per-battle rule still holds. The vehicle is the field this exists for, since the form never asks for it on the way in. A correction always goes back to the queue, so a video that was live comes down until it is approved again. A correction always goes back to the queue, so a video that was live comes down until it is approved again. 401 when signed out and no token is given, 403 on someone else's, 404 when submissions are unconfigured or the row is unknown, 409 when the correction lands on a battle we already hold.