ID-1324 Adjust response body of group sync endpoint

[Ghost-in-a-Jar]

Ticket: https://broadworkbench.atlassian.net/browse/ID-1324

What:

Changes the response body of the group sync endpoint to match what TDR integration tests expect.

Why:

When we made change to the sync logic it changed the response of the sync endpoint in a way we didn't foresee.

How:

Instead of an empty response, return a map of the group email to an empty list (of sync reports)

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PR checklist

• I've followed the instructions if I've made any changes to the API, especially if they're breaking changes
• I've filled out the Security Risk Assessment (requires Broad Internal network access) and attached the result to the JIRA ticket

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

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

See analysis details on SonarCloud