Remove the .NET 7.0 iOS TFMs and update the MAUI sample to disable server certificate validation on iOS to make testing easier

Directory.Build.props

@@ -72,8 +72,6 @@
 
     <NetCoreIOSTargetFrameworks
       Condition=" '$(NetCoreIOSTargetFrameworks)' == '' And '$(SupportsIOSPlatformTargeting)' == 'true' ">
-      net7.0-ios12.0;
-      net7.0-ios13.0;
       net8.0-ios12.0;
       net8.0-ios13.0
     </NetCoreIOSTargetFrameworks>

sandbox/OpenIddict.Sandbox.Maui.Client/MauiProgram.cs

@@ -1,4 +1,5 @@
 #if IOS || WINDOWS
+using System.Net.Http;
 using Microsoft.EntityFrameworkCore;
 using Microsoft.Extensions.Hosting;
 using Microsoft.Extensions.Hosting.Internal;
@@ -54,7 +55,14 @@ public static class MauiProgram
                 // assembly as a more specific user agent, which can be useful when dealing with
                 // providers that use the user agent as a way to throttle requests (e.g Reddit).
                 options.UseSystemNetHttp()
-                       .SetProductInformation(typeof(MauiProgram).Assembly);
+                       .SetProductInformation(typeof(MauiProgram).Assembly)
+#if IOS
+                       // Warning: server certificate validation is disabled to simplify testing the MAUI
+                       // application with the iOS simulator: in production, it SHOULD NEVER be disabled.
+                       .ConfigureHttpClientHandler("Local", handler => handler.ServerCertificateCustomValidationCallback =
+                           HttpClientHandler.DangerousAcceptAnyServerCertificateValidator)
+#endif
+                       ;
 
                 // Add a client registration matching the client application definition in the server project.
                 options.AddRegistration(new OpenIddictClientRegistration