Summary

Adds a new parser setting to allow duplicate normalized paths when they use different HTTP methods, resolving issues with real-world OpenAPI specs that technically violate the specification but can be safely handled.

Fixes #1590

Changes

• Add DisallowDuplicateMethodPaths setting (default: false for lenient mode)
• Allow duplicate paths when HTTP methods don't overlap
• Always reject same-method conflicts (e.g., two GETs on same path)
• Expose setting via gen.ParseOptions for YAML/JSON configuration

API Example

# Previously errored, now allowed by default:
paths:
  /pets/{petId}:
    get: ...      # GET /pets/:param
  /pets/{id}:
    post: ...     # POST /pets/:param (different method, different param name)

# Still rejected (same method conflict):
paths:
  /pets/{petId}:
    get: ...
  /pets/{id}:
    get: ...      # ERROR: duplicate GET

# Strict mode (opt-in):
parser_settings:
  disallow_duplicate_method_paths: true  # Rejects all duplicates

Testing

• 3 parser unit tests: allow different methods, reject same method, strict mode
• 1 generator integration test validating end-to-end behavior
• All existing tests pass

Notes

Breaking Change: None - default behavior is lenient (allows different-method duplicates). Users wanting strict validation can opt-in via configuration.