fix(GAT-8925): Fix incorrect config read on cohort expiry command

[equinoxmatt]

Describe your changes

The wrong config value was being used when calculating the expiry date for nhse sde.

Also created a test to cover the nhse sde approval on PUT /api/v1/cohort_requests/{id}

Issue ticket link

https://hdruk.atlassian.net/browse/GAT-8925

Environment / Configuration changes (if applicable)

Requires migrations being run?

If not using the pre-push hook. Confirm tests pass:

Checklist before requesting a review

• I have performed a self-review of my code
• I have added appropriate unit tests
• I have created mocks for unit tests (where appropriate)
• I have added appropriate Behat tests to confirm AC (if applicable)
• I have added Swagger annotations for new endpoints (if applicable)
• I have added audit logs for new operation logic (if applicable)
• I have added new environment variables to the .env.example file (if applicable)
• I have added new environment variables to terraform repository (if applicable)

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