Dapr authentication not working alongside Aspire and KeyCloak

As reported on Discord [here](https://discord.com/channels/778680217417809931/778680217417809934/1352554821290426459):

> I have and Aspire.Net 9.1 Project running under .net 9 Combined with the keycloak preview package for aspire. The Website and the service are using authentication with keycloak and are working. My problem is as soon as I am using Dapr authentication fails. It looks like the Dapr sidecars do not transport the token and I found absolutely no documentation of how to set this up in an Aspire environment.

This is the [preview Keycloak package](https://www.nuget.org/packages/Aspire.Keycloak.Authentication/9.1.0-preview.1.25121.10?_src=template) in question. It adds JwtBearer and OpenId Connect authentication to the project via a Keycloak.

The reporting user got two errors when calling the service with Dapr:
> 2025-03-21T09:17:46 fail: Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware[1]
2025-03-21T09:17:46 An unhandled exception has occurred while executing the request.
2025-03-21T09:17:46 Dapr.Client.InvocationException: An exception occurred while invoking method: 'weatherforecast' on app-id: 'weatherservice'
2025-03-21T09:17:46 ---> System.Net.Http.HttpRequestException: Response status code does not indicate success: 401 (Unauthorized).

and

> 2025-03-21T09:17:46 fail: Microsoft.AspNetCore.Server.Kestrel[13]
2025-03-21T09:17:46 Connection id "0HNB8A3D98IJ4", Request id "0HNB8A3D98IJ4:00000011": An unhandled exception was thrown by the application.
2025-03-21T09:17:46 Dapr.Client.InvocationException: An exception occurred while invoking method: 'weatherforecast' on app-id: 'weatherservice'
2025-03-21T09:17:46 ---> System.Net.Http.HttpRequestException: Response status code does not indicate success: 401 (Unauthorized).

As the reporter continued:
> To me it looks like that the Autorization Handler is not added to the call or not delivered.
For the HTTPClient I could call:

```cs
builder.Services.AddHttpClient(client =>
{
client.BaseAddress = new("https+http://weatherservice");
})
.AddHttpMessageHandler();
```

But they found no counterpart for Dapr, not an example using Authentication inside an Aspire project.