A plan as you sign it: named creators, all-in prices, totals, payment options, the fingerprint and the mandate's answer

allowed: whether this key's mandate lets it sign now; refusal: the reason and numbers when not (over_budget when the plan is over the campaign's budget, which no mandate can approve: remove a creator or have the brand raise the budget).

The plan over its campaign's budget: budget_cents, total_cents and over_by_cents, at current prices when a creator's price rose past the budget (the plan then keeps its earlier prices, so total_cents alone reads as within it). Null within the budget, with no budget, or once signed. Approval refuses it until a creator is removed or the budget is raised.