Do not return 409 for InvalidCastException

[jaredcnance]

This should be handled explictly and we should not assume any InvalidCastException should return 409. Often times this is a 500 error.

JsonApiDotNetCore/src/JsonApiDotNetCore/Internal/JsonApiExceptionFactory.cs

Lines 14 to 20 in c2cb69f

	// TODO: this is for mismatching type requests (e.g. posting an author to articles endpoint)
	// however, we can't actually guarantee that this is the source of this exception
	// we should probably use an action filter or when we improve the ContextGraph
	// we might be able to skip most of deserialization entirely by checking the JToken
	// directly
	if (exceptionType == typeof(InvalidCastException))
	return new JsonApiException(409, exception.Message, exception);