ordering - unclear error message when mandatory columns are empty

[diitaz93]

Describe the bug
A customer tried to submit a Pacbio orderform with some mandatory fields empty (see ticket 1002565). The specific fields were:

• Delivery
• Is the sample from a tumor
• Contact customer if QC fails
• Priority

The error that they got in the order portal was:

Which is not very informative.

To Reproduce
Steps to reproduce the behavior:

1. Download the orderform in the ticket mentioned above
2. Try submitting that order

Expected behavior
The error message should say at the very least that some mandatory fields are missing. Ideally it should show all the fields in which it was expecting data but were empty.