Apportionment structs/functions/tests

[stacktraceghost]

Resolves #2766
Resolves #2767

Changes:

• Brought back apportionment code

• Adjusted structs

  • As minimal as possible, not linked to Abacus
  • Implemented traits

• Reorganized code

  • Structure: split seat assignment and candidate nomination into folders
  • Renamed PoliticalGroup to List
  • Extracted DisplayFraction to Abacus domain layer

• Updated links to law articles

• Added newtypes

• Added apportionment crate to sigrid.yaml

• Moved backend/src/apportionment/*, frontend and other backend changes to separate branch (bring_back_apportionment_api) for future epic.

Not in scope: #2785

[github-actions]

Sigrid maintainability feedback

⏸️️ Your are still below your objective of 3.5 stars.

Show details

Sigrid compared your code against the baseline of 2026-02-05.

👍 What went well?

You fixed or improved 0 refactoring candidates.

👎 What could be better?

Unfortunately, 24 refactoring candidates were introduced or got worse.

Risk	System property	Location
🔴	Duplication (Introduced)	backend/src/domain/id.rs line 36-46 backend/apportionment/src/int_newtype_macro.rs line 12-22
🔴	Duplication (Introduced)	backend/apportionment/src/seat_assignment/residual_seat_assignment.rs line 125-130 backend/apportionment/src/seat_assignment/mod.rs line 132-137
🔴	Duplication (Introduced)	backend/apportionment/src/seat_assignment/residual_seat_assignment.rs line 108-113 backend/apportionment/src/seat_assignment/residual_seat_assignment.rs line 212-217
🔴	Unit Size (Introduced)	backend/apportionment/src/seat_assignment/mod.rs seat_assignment(T)
🔴	Unit Interfacing (Introduced)	backend/apportionment/src/seat_assignment/residual_seat_assignment.rs assign_remainder([ListStanding],u32,u32,u32,[SeatChangeStep],Option,any)
🟠	Unit Size (Introduced)	backend/apportionment/src/seat_assignment/residual_seat_assignment.rs assign_remainder([ListStanding],u32,u32,u32,[SeatChangeStep],Option,any)
🟠	Unit Size (Introduced)	backend/apportionment/src/seat_assignment/residual_seat_assignment.rs step_assign_remainder_using_largest_remainder([ListStanding],u32,[SeatChangeStep],[ListNumber])
🟠	Unit Size (Introduced)	backend/apportionment/src/seat_assignment/mod.rs reassign_residual_seat_for_absolute_majority(u32,u32,[T],[ListNumber],Vec<ListStanding>)
⚫️		+ 16 more

📚 Remaining technical debt

0 refactoring candidates didn't get better or worse, but are still present in the code you touched.

View this system in Sigrid to explore your technical debt

⭐️ Sigrid ratings

System property	System on 2026-02-05	Before changes	New/changed code
Volume	3.4	N/A	N/A
Duplication	3.6	5.5	4.5
Unit Size	2.2	5.5	2.5
Unit Complexity	3.2	5.5	3.9
Unit Interfacing	3.0	5.5	1.2
Module Coupling	3.4	N/A	3.0
Component Independence	2.0	N/A	N/A
Component Entanglement	2.4	N/A	N/A
Maintainability	2.9	5.5	3.2

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.37%. Comparing base (1e34853) to head (692d289).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2787      +/-   ##
==========================================
- Coverage   91.38%   91.37%   -0.01%     
==========================================
  Files         380      380              
  Lines       17661    17661              
  Branches     1987     1987              
==========================================
- Hits        16139    16138       -1     
  Misses       1424     1424              
- Partials       98       99       +1     

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[Lionqueen94]

@praseodym Should we already add the apportionment crate to sigrid.yml in this PR?

[praseodym]

@praseodym Should we already add the apportionment crate to sigrid.yml in this PR?

Yes!

[github-actions]

PDF Diff Summary

Comparing against base branch: main

File	Status
model-n-10-2.pdf	✅ No changes
model-na-14-2-bijlage1.pdf	✅ No changes
model-na-14-2.pdf	✅ No changes
model-na-31-2-bijlage1.pdf	✅ No changes
model-na-31-2-inlegvel.pdf	✅ No changes
model-na-31-2.pdf	✅ No changes
model-p-2a.pdf	✅ No changes

Ruben will do an extra check and make improvements next week