Applies credit memos to invoices in batch. Each application set contains one or more credit memos
and one or more invoices. Smart apply (null AmountToApply) and select apply (explicit amount) are
both supported per CM and per invoice.

Conditions per credit memo:

• Credit memo must have ApprovalStatus 'Approved'.
• Credit memo must not be fully credited (unapplied balance must be > 0).
• AmountToApply (if provided) must be > 0 and ≤ unapplied balance.

Conditions per invoice:

• Invoice must have ApprovalStatus 'Approved'.
• Invoice must have an outstanding balance (TotalDueAmount > 0 and PaymentStatus ≠ 'Paid').
• AmountToApply (if provided) must be > 0 and ≤ invoice TotalDueAmount.

Cross-set conditions:

• All CMs and invoices within a set must share the same Bill-To account (X-1).
• When all amounts are provided, sum of CM amounts must be ≤ sum of invoice amounts (X-2).

Effects of a successful application:

• Invoice TotalDueAmount is reduced; PaymentStatus transitions to 'Partially Paid' or 'Paid'.
• Credit memo AppliedAmount is increased; PaymentStatus transitions to 'Partially Credited' or 'Credited'.
• Invoice-side AR transaction (Credit) and credit memo-side AR transaction (Applied) are created per CM-Invoice pair.