Address PR #2645 review comments: improve type checking logic and use JsonNode.DeepEquals

[Copilot]

Pull Request

Description

Addresses review feedback on PR microsoft#2645 by replacing .NET 5+ specific Enum.IsDefined with clear iteration logic and updating test assertions to use structural JSON comparison instead of string comparison.

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Other (please describe):

Related Issue(s)

Addresses review comments on https://github.com/microsoft/OpenAPI.NET/pull/2645/files

Changes Made

• Replaced System.Enum.IsDefined(commonType) with clear iteration logic that explicitly checks if all schemas have the same type
  • Avoids .NET 5+ dependency and trimming issues
  • Uses & ~JsonSchemaType.Null bitwise operator to remove Null flag from type comparison, consistent with existing patterns in the class
  • More readable and maintainable code
• Updated 7 test methods to use JsonNode.DeepEquals instead of string comparison with MakeLineBreaksEnvironmentNeutral()
  • More robust structural comparison
  • Platform-agnostic line ending handling

Testing

• Unit tests added/updated
• Integration tests added/updated
• Manual testing performed
• All existing tests pass

Checklist

• My code follows the code style of this project
• I have performed a self-review of my own code
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

Versions applicability

• My change applies to the version 1.X of the library, if so PR link:
• My change applies to the version 2.X of the library, if so PR link:
• My change applies to the version 3.X of the library, if so PR link:
• I have evaluated the applicability of my change against the other versions above.

See the contributing guidelines for more information about how patches are applied across multiple versions.

Additional Notes

All 927 tests pass. Changes maintain backward compatibility while improving cross-framework support and code readability. The implementation uses the established bitwise pattern from the class for handling null flags.

Original prompt

Can you fix the comments on the PR https://github.com/microsoft/OpenAPI.NET/pull/2645/files

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[desjoerd]

See my comment on on the first type logic.

You should still remove null from the equation. You can still do that with a bit wise operator as that is done at more places in this class.

[Copilot]

See my comment on on the first type logic.

You should still remove null from the equation. You can still do that with a bit wise operator as that is done at more places in this class.

Updated to use & ~JsonSchemaType.Null bitwise operator to remove the Null flag from type comparison, consistent with other usage in the class. Commit: 3f2402f