[DT-2757] Ensure institutional Certification files are saved on appropriate dataset updates

[otchet-broad]

Addresses

https://broadworkbench.atlassian.net/browse/DT-2757

Summary

Updates to documents were only being saved for the first dataset on a study.

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[otchet-broad]

This is the core of the bug. When multiple datasets are updated, we can have multiple files submitted. Assuming the files key was always consentGroups[**0**].nihInstitutionalCertificationFile is incorrect. The update payload might be just a change for consentGroup[5], or a case where multiple consentGroup entries are updated at the same time.

Given this bug I've made https://broadworkbench.atlassian.net/browse/DT-2759

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
83.3% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[otchet-broad]

Passing the studyUpdate files into the dataset updates (and inserts ~L271) was also problematic. The files would be uploaded to GCS but the FSOs wouldn't be recorded.