Add default Validation Rule for path operations to not have a request body

[martincostello]

Is your feature request related to a problem? Please describe.

I found a bug in ASP.NET Core where invalid schema references were being generated that are circular references: dotnet/aspnetcore#63090

While doing that, I noticed a separate issue where some operations in a test document for HTTP GET include a request body.

editor.swagger.io detects these issues, but the default validation ruleset does not.

Describe the solution you'd like

A validation rule for paths that verify that OpenAPI schema references are valid.

Describe alternatives you've considered

Write code to manually validate HTTP GET operations do not have a request body.

Additional context

• [OpenAPI] Invalid schema references generated dotnet/aspnetcore#63090
• Add default Validation Rule(s) for schema reference validity #2453

[darrelmiller]

@martincostello We can create the rule, but we can't add it to the default rules because it isn't a MUST in HTTP. This is reflected in the OpenAPI specification

In other cases where the HTTP spec is vague (such as GET, HEAD and DELETE), requestBody is permitted but does not have well-defined semantics and SHOULD be avoided if possible.

https://spec.openapis.org/oas/v3.1.1.html#fixed-fields-7