HttpContext.User.Identity 何时设置

HttpContext.User.Identity 是什么？

csharp
using Microsoft.AspNetCore.Mvc;
[ApiController]
[Route("api/[controller]")]
public class UserController : ControllerBase
{
    [HttpGet]
    [Authorize] // 需要身份验证才能访问该方法
    public IActionResult GetUserInfo()
    {
        var username = HttpContext.User.Identity.Name;
        var isAuthenticated = HttpContext.User.Identity.IsAuthenticated;
        var authenticationType = HttpContext.User.Identity.AuthenticationType;
        // 执行一些操作，例如获取用户信息、授权检查等
        // 返回用户信息
        return Ok(new
        {
            Username = username,
            IsAuthenticated = isAuthenticated,
            AuthenticationType = authenticationType
        });
    }
}