Pending and authorized gifts versus subscription usage

For GiveCampus reporting.

Do not assume subscription usage is paid-only. The usage collectors include authorized and pending_authorization states as well as paid and certain later states when captured_at falls within the usage window. The displayed remaining balance also depends on billing synchronization, contract terms and major-gift treatment. Billing must reconcile the actual subscription snapshot and contract before confirming its remaining allowance or whether invoking a major-gift clause is appropriate.