fix(models): reject RFC 6570 operators for <3.2

[mdaneri]

Pull Request

Description

Reject RFC 6570 URI template operators (e.g. {+path}, {path*}, {?q}) in path keys when serializing OpenAPI <= 3.1. These operators are only valid starting in OpenAPI 3.2.

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)

Fixes #2704

Changes Made

• Throw OpenApiException if an OpenApiPaths key contains RFC 6570 operators when targeting OpenAPI 2.0/3.0/3.1.
• Add unit tests for operator paths ({+var}, {var*}) and a non-operator control case.

Testing

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

Ran:

• dotnet test test/Microsoft.OpenApi.Tests/Microsoft.OpenApi.Tests.csproj --filter FullyQualifiedName~Microsoft.OpenApi.Tests.Models.OpenApiPathsTests

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.

Additional Notes

None.

[baywet]

See my comments here #2704 (comment)