Access another part of a body request sent to a c# .net core app

Im just starting to learn C# and building a service for a simple project. I am using Hasura as my API (GraphQL) and sending a Hasura action (POST webhook) to my C# app. It works by when the action mutation happens it sends the POST request. The issue im having is that the format of the request has a complex body.

The app works fine with just using Postman as the response is simple. The response for the Hasura is below.

  request_query: 'mutation Mutation {\n' +
    '  validateName(card: "ADSADSA", email: "ADSADSA", name: "DASDADAS") {\n' +
    '    card\n' +
    '    name\n' +
    '    email\n' +
    '  }\n' +
    '}\n' +
    '\n' +
    'query MyQuery {\n' +
    '  users {\n' +
    '    card\n' +
    '    email\n' +
    '    id\n' +
    '    name\n' +
    '  }\n' +
    '}\n',
  session_variables: { 'x-hasura-role': 'admin' },
  input: { card: 'ADSADSA', email: 'ADSADSA', name: 'DASDADAS' },
  action: { name: 'validateName' }
}

This is my current C# code.

var builder = WebApplication.CreateBuilder(args);
var app = builder.Build();

app.UseHttpLogging(); 


app.MapPost("/validateName", async (User user) => {

Console.WriteLine(user.name);
var validateUser = new User();
validateUser.name = user.name?.ToLower();
validateUser.email = user.email?.ToLower();
validateUser.card = user.card?.ToLower();

return Results.Json(validateUser);
});

app.Run();

class User
{
    public string? name { get; set; } 
    public string? email { get; set; }
    public string? card { get; set; }
}

Firstly I would like to know how do I see the response in C#. Secondly how would i access the input of the body as this is where the key data I need.

Thanks.