Bugfix for invoice unit tests and model.js:
- invoice.js: date format for date fields (invoice) set to YYYYMMDD instead of YYYYMMDDThhmmss (in select statement)
- model.js: FIXED when findById does not find record, it would return rows:1 => Fixed, returns rows:0 in this case now
- /test/invoices.js: FIXED wrong http verb (POST instead of GET) in retrieveInvoice led to very strange error messages, even in other tests functions *PHEW!!*
Now all 60 tests are green!