DM-51789: Add support for looking up column references by name

[JeremyMcCormick]

This updates Felis to support referencing of columns by their name instead of their ID, described in RFC-1111. The ID lookup is also supported for backward compatibility, at least for the deprecation period.

The primaryKey field still uses the ID for now. This will be resolved on a separate PR for DM-46055.

Checklist

• Ran Jenkins
• Added a release note for user-visible changes to docs/changes

[codecov]

Codecov Report

❌ Patch coverage is 97.11538% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 92.01%. Comparing base (610ed3f) to head (f49cb6e).
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
python/felis/datamodel.py	97.14%	1 Missing and 1 partial ⚠️
python/felis/metadata.py	95.83%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #189      +/-   ##
==========================================
+ Coverage   91.89%   92.01%   +0.12%     
==========================================
  Files          13       13              
  Lines        2060     2116      +56     
  Branches      299      313      +14     
==========================================
+ Hits         1893     1947      +54     
- Misses        109      110       +1     
- Partials       58       59       +1     

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[Copilot]

Pull request overview

Adds name-based resolution of column references across the Felis datamodel and downstream consumers, while preserving backward compatibility with legacy global column IDs.

Changes:

• Introduces name-first column resolution (Table._find_column) and updates schema validation for constraints/indexes.
• Adds ForeignKeyReference to support a name-based foreign key target (reference) alongside legacy referencedColumns.
• Updates SQLAlchemy metadata builder, TAP_SCHEMA loader, and test fixtures to use name-based references.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
tests/test_metadata.py	Updates metadata assertions to resolve constraint/index column refs via name-first lookup.
tests/test_datamodel.py	Adds tests covering name-based lookup for column groups, indexes, and foreign keys (including reference).
tests/data/sales.yaml	Migrates fixture constraints to name-based column refs and adds new constraints using reference.
python/felis/tap_schema.py	Resolves foreign keys using name-based refs (and legacy fallback) when generating TAP_SCHEMA keys/key_columns rows.
python/felis/metadata.py	Switches metadata building to resolve columns by name-first lookup and maps Felis objects to SQLAlchemy objects by identity.
python/felis/datamodel.py	Adds ForeignKeyReference, name-first column lookup, FK exclusivity checks, and schema validation for index/constraint refs.

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