Mark a reimbursement as paid outside Mercury

Record that the submitter was paid outside Mercury, for example by check or payroll. Mercury won’t pay the reimbursement, and its payment status reads as paidOutsideMercury. Denied or canceled reimbursements, and ones with a Mercury payment in progress or completed, can’t be marked. The optional note is recorded as a reviewer comment. Approving or denying the reimbursement afterwards undoes the mark.