BCDA-5938: Decrease code complexity for function getNewAndExistingBeneficiaries

[4ell0]

Fixes BCDA-5938

Decrease code complexity for function getNewAndExistingBeneficiaries and its tests

• move logic in getNewAndExistingBeneficiaries into smaller functions
• update tests

Security Implications

• new software dependencies

• security controls or supporting software altered

• new data stored or transmitted

• security checklist is completed for this change

• requires more information or team discussion to evaluate security implications

• no PHI/PII is affected by this change

Acceptance Validation

Feedback Requested

[codecov-commenter]

Codecov Report

Merging #803 (c8e96d0) into master (271467d) will decrease coverage by 0.02%.
The diff coverage is 75.86%.

@@            Coverage Diff             @@
##           master     #803      +/-   ##
==========================================
- Coverage   75.04%   75.01%   -0.03%     
==========================================
  Files          89       89              
  Lines       10234    10259      +25     
==========================================
+ Hits         7680     7696      +16     
- Misses       1950     1956       +6     
- Partials      604      607       +3     

Impacted Files	Coverage Δ
bcda/service/service.go	83.05% <75.86%> (+0.31%)	⬆️
bcda/models/fhir/alr/v2/group.go	87.79% <0.00%> (-1.75%)	⬇️
bcda/models/fhir/alr/v1/group.go	88.00% <0.00%> (-1.72%)	⬇️

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