Schemas that make much use of $ref can cause Newtonsoft to if schema validation fails

[idg10]

If Menes detects that input fails schema validation, it attempts to produce a 400 response that describes the problem, and which includes a copy of the schema that has been violated.

At some point (we think somewhere mid 2022) the Microsoft OpenAPI libraries started including reference details where $ref has been used, that end up including a pointer back to the whole OpenAPI doc. This causes Menes to crash because we end up with loops when trying to serialize the schema. But in any case, we shouldn't even be trying to copy the entire open API doc.

We need to work out how to stop it doing this. That might entail using the OpenApi library's built in functionality for serializing schemas. Or it might involve customizing how we serialize the thing.

First, we need to make the problem repro in the PetStore project, and then fix that.

[idg10]

Looks like this behaviour came in with an update to the Microsoft OpenAPI libraries, and then was fixed in a later release, so it no longer repros. However, we're no longer confidence that the code serializing the schema in the error response is doing things the best way. Look into whether we should use a different way to serialize the schema into the response.