-the functionality was already in place for a transactions/invoices relationship endpoint in the last PR; this provides a test for that
-all tests + spec harness passes
-the relationship endpoint tests for 'invoice_items' previously had their own file, I moved them to the 'invoice_items_request_spec.rb' under a new context which is where the other tests have them
-the functionality was already in place for a transactions/invoices relationship endpoint in the last PR; this provides a test for that -all tests + spec harness passes -the relationship endpoint tests for 'invoice_items' previously had their own file, I moved them to the 'invoice_items_request_spec.rb' under a new context which is where the other tests have them