Setup JWT from headers to be used by default in HttpClient - asp.net-core

Question

I use .NET 6 and add HttpClient in Program.cs like this:
builder.Services.AddHttpClient<IUserClient, UserClient>(client =>
{
client.BaseAddress = new Uri(builder.Configuration["Clients:UserBaseUrl"]);
});
In my onion architecture when I want to create an order a request is coming to OrderService.API and to check userId is correct in IUserService from OrderService.BL I call user microservice API with the help of registered HttpClient. So the problem is that for now, I need to transfer JWT to the business logic layer via method parameters.
var createdOrder = await _orderService.Add(model.MapToDto(), HttpContext.Request.Headers["Authorization"]);
I don't like it because, for every method using the HttpClient, it's necessary to provide an extra parameter. I think maybe there is a way to set up HttpClient default authentication during the current request.
I tried to setup default request headers during HttpClient registration:
builder.Services.AddHttpClient<IUserClient, UserClient>(client =>
{
client.BaseAddress = new Uri(builder.Configuration["Clients:UserBaseUrl"]);
client.DefaultRequestHeaders.Add("Authorization", token); // setup token
});
but I don't know how to get JWT from HttpRequest headers there.
Additionally, I thought maybe I can set up the header for HttpClient in some additional BaseController which would be nested by any other my controller but it doesn't seem to be a great solution.
Maybe there is a way for middleware use but as I understand we handle an incoming request to OrderService and can't handle outcoming requests from HttpClient.
So would be grateful for any of your ideas!

Answer 1

Thanks to #Rena who provided a link to an existing similar problem: https://stackoverflow.com/a/62324677/11398810
So I created a message helper like this and it seems work for me:
public sealed class HttpClientsAuthHelper : DelegatingHandler
{
private readonly IHttpContextAccessor _accessor;
public HttpClientsAuthHelper(IHttpContextAccessor accessor)
{
_accessor = accessor;
}
protected override async Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
{
var token = _accessor.HttpContext.Request.Headers["Authorization"].First();
request.Headers.Add("Authorization", token);
return await base.SendAsync(request, cancellationToken);
}
}
And added these lines to Program.cs:
builder.Services.TryAddSingleton<IHttpContextAccessor, HttpContextAccessor>();
builder.Services.AddTransient<HttpClientsAuthHelper>();
builder.Services.AddHttpClient<IUserClient, UserClient>(client =>
{
client.BaseAddress = new Uri(builder.Configuration["Clients:UserBaseUrl"]);
}).AddHttpMessageHandler<HttpClientsAuthHelper>();
builder.Services.AddHttpClient<IProductClient, ProductClient>(client =>
{
client.BaseAddress = new Uri(builder.Configuration["Clients:ProductBaseUrl"]);
}).AddHttpMessageHandler<HttpClientsAuthHelper>();
I'm not sure how correct such approach so I'll dive a bit into this logic later =)