Allow duplicate taxonomy names

[galvana]

Ticket ENG-1963

Description Of Changes

This PR enables duplicate taxonomy names across the taxonomy system (data categories, data uses, data subjects, and custom taxonomy elements). Previously, both fides_key and name had to be unique within each taxonomy type. Now, only fides_key must be unique, allowing multiple elements to share the same name as long as they have different keys or parent hierarchies.

This change better supports real-world taxonomy use cases where:

• Different branches of a hierarchical taxonomy may need the same semantic names (e.g., "Employee" under different regional parents)
• Multiple data subjects may share common names but represent different entities (e.g., "Customer" for different business units)
• Taxonomy migrations and imports from different sources may introduce naming conflicts that are semantically acceptable

The uniqueness constraint is now enforced solely on fides_key within each taxonomy type, while names can be duplicated freely.

Code Changes

• Modified DataCategory, DataSubject, and DataUse models in sql_models.py to override create() and update() methods, skipping name uniqueness checks while enforcing fides_key uniqueness
• Modified TaxonomyElement model in taxonomy.py to override create() and update() methods with the same logic for custom taxonomies
• Updated error handling in generic_overrides.py API endpoints to return more specific error messages from KeyOrNameAlreadyExists exceptions

Steps to Confirm

1. Follow the testing steps in https://github.com/ethyca/fidesplus/pull/2793

Pre-Merge Checklist

• Issue requirements met
• All CI pipelines succeeded
• CHANGELOG.md updated
  • Add a db-migration This indicates that a change includes a database migration label to the entry if your change includes a DB migration
  • Add a high-risk This issue suggests changes that have a high-probability of breaking existing code label to the entry if your change includes a high-risk change (i.e. potential for performance impact or unexpected regression) that should be flagged
  • Updates unreleased work already in Changelog, no new entry necessary
• UX feedback:
  • All UX related changes have been reviewed by a designer
  • No UX review needed
• Followup issues:
  • Followup issues created
  • No followup issues
• Database migrations:
  • Ensure that your downrev is up to date with the latest revision on main
  • Ensure that your downgrade() migration is correct and works
    • If a downgrade migration is not possible for this change, please call this out in the PR description!
  • No migrations
• Documentation:
  • Documentation complete, PR opened in fidesdocs
  • Documentation issue created in fidesdocs
  • If there are any new client scopes created as part of the pull request, remember to update public-facing documentation that references our scope registry
  • No documentation updates required

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[codecov]

Codecov Report

❌ Patch coverage is 79.66102% with 12 lines in your changes missing coverage. Please review.
✅ Project coverage is 87.31%. Comparing base (69e950e) to head (3ce5596).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/fides/api/models/taxonomy.py	37.50%	8 Missing and 2 partials ⚠️
src/fides/api/models/sql_models.py	95.00%	0 Missing and 2 partials ⚠️

❌ Your patch status has failed because the patch coverage (79.66%) is below the target coverage (100.00%). You can increase the patch coverage or adjust the target coverage.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6971      +/-   ##
==========================================
- Coverage   87.33%   87.31%   -0.02%     
==========================================
  Files         525      525              
  Lines       34458    34512      +54     
  Branches     3967     3984      +17     
==========================================
+ Hits        30093    30134      +41     
- Misses       3501     3511      +10     
- Partials      864      867       +3     

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[greptile-apps]

Greptile Overview

Greptile Summary

This PR removes the name uniqueness constraint from taxonomy elements (data categories, data uses, data subjects, and custom taxonomies), allowing multiple elements to share the same name as long as their fides_key values are unique. The implementation overrides the create() and update() methods in the model classes to skip name validation while enforcing fides_key uniqueness.

Key changes:

• Modified DataCategory, DataSubject, and DataUse models to override create/update methods with check_name=False
• Modified TaxonomyElement model with the same pattern for custom taxonomies
• Updated API error handling to use exception messages directly for better error reporting
• Added comprehensive test coverage for duplicate name scenarios across all taxonomy types
• No database migration required since the change is purely at the application logic level (no schema changes)

Confidence Score: 4/5

• This PR is safe to merge with minor style improvements recommended
• The implementation is straightforward and well-tested. The core logic correctly removes name uniqueness checks while maintaining fides_key uniqueness. Minor style issues exist with redundant filter conditions in update methods that don't affect functionality but could be simplified for clarity.
• No files require special attention

Important Files Changed

File Analysis

Filename	Score	Overview
src/fides/api/models/sql_models.py	4/5	Overrides create() and update() methods for DataCategory, DataSubject, and DataUse to allow duplicate names while enforcing fides_key uniqueness. Logic is sound with one minor redundancy issue in update methods.
src/fides/api/models/taxonomy.py	5/5	Overrides create() and update() methods for TaxonomyElement to skip name uniqueness checks. Implementation correctly handles taxonomy_type scoping for custom taxonomies.
src/fides/api/api/v1/endpoints/generic_overrides.py	5/5	Updates error handling to use the exception message directly via str(e), providing more accurate error messages to API consumers.
tests/service/test_taxonomy_service.py	5/5	Adds comprehensive test coverage for duplicate name scenarios across all taxonomy types, including create and update operations. Tests verify both success and failure cases.

[greptile-apps]

_{4 files reviewed, 3 comments}

_{Edit Code Review Agent Settings | Greptile}

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[JadeCara]

Updated the greptile's suggestions and tested locally. I was not able to add duplicate sibling names as expected.