Validation: Improve finding reference controls in `findings` workbook

[jadudm]

Consider the following:

award_reference	reference_number	type_requirement	is_modified_opinion	is_other_findings	is_material_weakness	is_significant_deficiency	is_other_matters	is_questioned_costs	is_repeat_finding	prior_finding_ref_numbers
AWARD-0003	2023-001	L	N	N	Y	N	N	N	Y	2022-001
AWARD-0003	2023-002	L	N	N	Y	N	N	N	Y	2022-001
AWARD-0004	2023-001	L	N	N	N	Y	N	N	N	N/A

Award 3 has findings reference 1 and 2. This is good.

Award 4 has finding reference 1. This is appropriate; a single finding can apply to multiple awards.

What does not make sense is that the auditor findings are different for row 1 and row 3. That is, finding reference 2023-001 is being described in two different ways. In the case of finding 001, is_material_weakness is both Y and N.

This can be seen in report 2023-05-GSAFAC-0000027356.

Validation improvement

Our data validation on this sheet should ensure that a given finding reference (e.g. 2023-001) has the same values in every instance.

For error reporting, we should report the first instance we find (in this case, row 1), and report each deviance as a separate error. So, we would expect one error to be reported back in this case, for row three. Something akin to:

On row 1, you reported 2023-001 as ..., and on row 3, you reported it as .... The FAC cannot accept one finding reference with different <insert word...>

### Tasks
- [ ] Determine correct language for the properties associated with a finding reference.
- [ ] Implement validation
- [ ] Add a findings sheet to `should pass` and `should fail` in the test suite
- [ ] Document this change as part of the next monthly update