Configures forwarded headers options

Configures the forwarded headers options to accept all forwarded headers,
clears the default known networks and proxies, and adds a new known IP network
to allow any IP address. This is necessary to handle requests from proxies
and load balancers correctly.

Source/ProofOfConcept/Program.cs

@@ -1,3 +1,4 @@
+using System.Net;
 using System.Text;
 using System.Text.Json;
 using Microsoft.AspNetCore.Authentication;
@@ -13,6 +14,7 @@ using ProofOfConcept.Models;
 using ProofOfConcept.Services;
 using ProofOfConcept.Utilities;
 using SzakatsA.Result;
+using IPNetwork = System.Net.IPNetwork;
 
 Microsoft.IdentityModel.Logging.IdentityModelEventSource.ShowPII = true;
 
@@ -150,8 +152,9 @@ builder.Services.AddHostedService<MQTTClient>();
 WebApplication app = builder.Build();
 
 ForwardedHeadersOptions forwardedHeadersOptions = new ForwardedHeadersOptions() { ForwardedHeaders = ForwardedHeaders.All };
-forwardedHeadersOptions.KnownNetworks.Clear();
+forwardedHeadersOptions.KnownIPNetworks.Clear();
 forwardedHeadersOptions.KnownProxies.Clear();
+forwardedHeadersOptions.KnownIPNetworks.Add(new IPNetwork(IPAddress.Any, 0));
 forwardedHeadersOptions.ForwardLimit = null;            // allow entire header chain, even if single hop
 forwardedHeadersOptions.RequireHeaderSymmetry = false;  // don’t bail if headers aren’t “perfectly” paired