Add unit test coverage to Aggregate Work

[exalate-issue-sync]

Sonar cloud identified gaps in unit test coverage on https://fecgov.atlassian.net/browse/FECFILE-2726 => https://sonarcloud.io/component_measures?id=fecgov_fecfile-web-api&branch=feature%2F2726-balanced_aggregation&metric=new_coverage&view=list.

Go through the gaps and create new tests to verify the functionality in those blocks.

An example of line that are ok to ignore are class level viewset code.

A good candidate for adding coverage is utils_aggregation_service.py

Make a followup ticket with any left over opportunities.

QA Notes

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DEV Notes

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Design

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See full ticket and images here: FECFILE-2911