SIN Check Response - Under Review

We currently treat SIN Check code 2 "under review" as not Valid. ESDC will follow up with a response in a .ISR file after a manual review. Currently, SIMS will create a second record in the student's sin validations table.
Results in multiple emails to student re updates to their SIN without any actual response (Pass 1 / Fail 3/4)

**Acceptance Criteria**
- [ ] Different action on Response 2? No email to student on response 2 since we expect a second response?

**Additional Context**

CSLP Status - CSLP Status description
1 - Passed Electronic or Manual Validation
2 - Under Review
3 - Rejected because SIN is invalid (has not been issued, has been cancelled or has been issued to completely different person)
4 - Rejected because SIN and associated data (Name, birthdate, gender) are not an exact match. One or all of the associated data items is sufficiently different from what is on the SIN Registry to put the validity in question
5 - Fraud
6 - Abandoned

Start by locating the SIN Check response handling, the SIN validations table update, and the student email notification path in SIMS. Trace how response code 2 and the later .ISR response are processed, then confirm the intended behavior with maintainers because the acceptance criterion is still phrased as a question. Done means the agreed response-2 behavior is implemented without duplicate records or premature student emails.

Written by the indexing model from the issue text.