feat: Allow users to set custom rule names

[AndreasAlbertQC]

Motivation

Addresses part of #122

Changes

• Added name argument to dy.rule, which allows users to set a custom name that will show up in any failure outputs.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (573b564) to head (5a6ce9e).

Additional details and impacted files

@@            Coverage Diff            @@
##              main      #274   +/-   ##
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  Coverage   100.00%   100.00%           
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  Files           54        54           
  Lines         3125      3129    +4     
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+ Hits          3125      3129    +4     

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[Copilot]

Pull request overview

This PR adds a name parameter to the @dy.rule() decorator, allowing users to specify custom, user-friendly names for validation rules that will appear in failure reports. This addresses part of issue #122, which requested the ability to assign friendly names to rules for better failure reporting.

Changes:

• Added optional name parameter to @dy.rule() decorator for custom rule naming
• Implemented validation to prevent duplicate rule names and reserved name conflicts (e.g., "primary_key")
• Added tests for custom rule names in both regular and group rules, plus error cases

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 3 comments.

File	Description
dataframely/_rule.py	Added name parameter to RuleFactory.__init__() and rule() decorator with updated docstring
dataframely/_base_schema.py	Updated metadata extraction to use custom names, added validation for duplicate and reserved names
tests/schema/test_rule_implementation.py	Added tests for illegal rule names (reserved "primary_key") and duplicate custom names
tests/schema/test_filter.py	Added tests verifying custom rule names appear correctly in FailureInfo.counts() for both regular and group rules

[borchero]

I'm not sure you can answer that question because you didn't write the initial issue report... 😄 but what's the rationale of assigning custom names to rules but not being able to provide custom names to column-level checks 🤔