Validation, is it even working ?

I've created a class, below, which has been decorated to set the type and the maximum length.

public class Test
{
[OpenApiProperty(Nullable = true, Description = "The unique message id of the request")]
[DataType(DataType.Text)]
[StringLength(10, MinimumLength = 1, ErrorMessage = "Eeeek")]
public string ExternalRef { get; set; }
}

In the progam.cs if I set the Openapi version to Version 2

var options = new OpenApiConfigurationOptions()
{
OpenApiVersion = OpenApiVersionType.V2,
}

The Swagger GUI will let me enter a string up to the Maximum length, and pass the call to to the azure function. :)
If I exceed the Maximum length the the Swagger GUI does nothing, no errors or change of colour, nothing. :(

If I update the OpenApiVersion to Version 3
Then every time, whether the string is shorter or longer than the maximum length the call will be passed to the azure function :(

Just for completeness my function is below

[Function("Function2")]
[OpenApiOperation(operationId: "Function2")]
[OpenApiRequestBody(contentType: "application/json", bodyType: typeof(Test), Description = "Test Object", Required = true)]
[OpenApiResponseWithBody(statusCode: HttpStatusCode.OK, contentType: "text/plain", bodyType: typeof(string), Description = "The OK response")]
public HttpResponseData Function2([HttpTrigger(AuthorizationLevel.Anonymous, "post")] HttpRequestData req)
{
_logger.LogInformation("C# HTTP trigger function processed a request.");

using var bodyReader = new StreamReader(req.Body);
var body = bodyReader.ReadToEndAsync().Result;

var data = JsonConvert.DeserializeObject(body);

var response = req.CreateResponse(HttpStatusCode.OK);
response.WriteStringAsync("Hello!!! " + data.ExternalRef);
return response;
}

This is a Isolated Azure Function V4 .Net 8

What I'd like to know:-
1, How do I set my openapi configuration so that the swagger GUI obeys the schema restrictions.
2, How do I set the openapi configuration so that the swagger GUI will indicate that something is wrong.

Thanks