How to manually generate authentication cookie in asp.net core?

Question

I want to manually generate the authentication cookie string on the server side, that is generated by ASP .NET core when you have setup cookie authentication middleware and you sign-in the user using SignInAsync(this HttpContext context, string? scheme, ClaimsPrincipal principal). I am using a REST Client to make calls to API server. The APIs use cookie authentication. There is a use-case where once I receive a SAML response from IDP, there is an initial call I need to make to the API to get the user details. For that purpose I need to set the cookie in the request.

I am using ASP .NET Core 5 with cookie authentication setup in the Startup.cs file. It is typical cookie authentication middleware.

Below is sample code of what I am trying to do:

using MyProvider.Saml2Component;
using Microsoft.AspNetCore.Authentication;
using Microsoft.AspNetCore.Authentication.Cookies;
using Microsoft.AspNetCore.Authorization;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc;
using Microsoft.Extensions.Logging;
using Newtonsoft.Json;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Net.Http;
using System.Security.Claims;
using System.Threading.Tasks;


    [HttpPost]
    public async Task<IActionResult> SamlCallBack()
    {
        var samlResult = await _samlServiceProvider.ReceiveSsoAsync().ConfigureAwait(false);
        if (samlResult != null)
        {
            var email = samlResult.Attributes.FirstOrDefault(e => e.Name == "email").ToString();
            var id = samlResult.Attributes.FirstOrDefault(e => e.Name == "guid").ToString();

            var claims = new List<Claim>();

            if (!string.IsNullOrEmpty(email))
            {
                claims.Add(new Claim(ClaimTypes.Email, email));
            }

            if (!string.IsNullOrEmpty(id))
            {
                claims.Add(new Claim("SsoId", id));
            }

            var baseAddress = new Uri("http://example.com");
            var cookieContainer = new CookieContainer();
            using (var handler = new HttpClientHandler() { CookieContainer = cookieContainer })
            using (var client = new HttpClient(handler) { BaseAddress = baseAddress })
            {
                //How to get authentication cookie value here

                var ticket = GetSigninCookie(claims);
                cookieContainer.Add(baseAddress, new Cookie("CookieName", ticket));
                var result = await client.PostAsync("/user", null);
                result.EnsureSuccessStatusCode();
                var userDetails = await result.Content.ReadAsAsync<UserDetails>();
                var identity = new ClaimsIdentity();

                var signInClaims = new List<Claim>
                {
                    new Claim(ClaimTypes.NameIdentifier, userDetails.Id.ToString()),
                    new Claim("CompanyId", userDetails.CompanyId.ToString()),
                    new Claim(ClaimTypes.Name, userDetails.UserName)
                };
                identity.AddClaims(signInClaims);
                await HttpContext.SignInAsync(CookieAuthenticationDefaults.AuthenticationScheme, new ClaimsPrincipal(identity));
                return RedirectToAction("Index", "Home");
            }


        }

        return View();
    }

    private string GetSigninCookie(List<Claim> claims)
    {
        throw new NotImplementedException();
    }