Withdraw Ad Consent

Ad measurement turned off (Reject all, Cookie settings, a Reject during signup, or GPC on every page): deletes the signed-in account's ad record, and only that one. It takes no parameters. Signed out there's nothing it can identify, so it deletes nothing and says so (signed_in false); the browser drops its own note either way. JSON only, so a plain cross-site form can't post it. A failure is a 5xx, and the page says the record isn't deleted.