Domain blocks: suspend, silence, reject media

DomainBlock (domain, severity, reject-media, public and private comment)
covers the domain and its subdomains. Admins manage them under
/clientapi/admin/domainblocks/{list,insert,delete}; the set is kept in
memory, reloaded on every change and at most five minutes stale.

A suspended domain is refused by FederationHttp.IsAllowed, so nothing is
fetched from it and no job delivers to it, and the inbox drops its
activities with a 202 before fetching any key. Reject-media strips the
attachments of posts from that domain. Silence is recorded for the
timelines and notifications that arrive in P1.2.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_012CzABvBkbcFqoHdmi8b9WB

PrivaPub.Tests/Infrastructure/FederationHttpTests.cs

@@ -6,7 +6,9 @@ using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Logging.Abstractions;
 using Microsoft.Extensions.Options;
 
+using PrivaPub.Federation.Moderation;
 using PrivaPub.Infrastructure.Http;
+using PrivaPub.Models.Federation;
 
 namespace PrivaPub.Tests.Infrastructure
 {
@@ -39,7 +41,7 @@ namespace PrivaPub.Tests.Infrastructure
 				.ConfigurePrimaryHttpMessageHandler(() => SafeHttpHandlerFactory.Create(options));
 			var provider = services.BuildServiceProvider();
 			return new FederationHttp(provider.GetRequiredService<IHttpClientFactory>(), new MemoryCache(new MemoryCacheOptions()),
-				new StaticOptionsMonitor(options), NullLogger<FederationHttp>.Instance);
+				new StaticOptionsMonitor(options), new StaticBlocks(), NullLogger<FederationHttp>.Instance);
 		}
 
 		[Fact]
@@ -91,6 +93,29 @@ namespace PrivaPub.Tests.Infrastructure
 		public void IsAllowed_takes_https_dns_names_only(string url, bool allowed) =>
 			Assert.Equal(allowed, Client(allowTestNetwork: false).IsAllowed(new Uri(url)));
 
+		[Fact]
+		public void IsAllowed_refuses_a_suspended_domain_and_its_subdomains()
+		{
+			var http = new FederationHttp(new ServiceCollection().AddHttpClient().BuildServiceProvider().GetRequiredService<IHttpClientFactory>(),
+				new MemoryCache(new MemoryCacheOptions()), new StaticOptionsMonitor(new FederationOptions()), new StaticBlocks("evil.example"),
+				NullLogger<FederationHttp>.Instance);
+
+			Assert.False(http.IsAllowed(new Uri("https://evil.example/users/x")));
+			Assert.False(http.IsAllowed(new Uri("https://cdn.evil.example/a.png")));
+			Assert.True(http.IsAllowed(new Uri("https://notevil.example/users/x")));
+		}
+
+		sealed class StaticBlocks : IDomainBlocks
+		{
+			readonly string[] _suspended;
+			public StaticBlocks(params string[] suspended) => _suspended = suspended;
+			public DomainBlock Find(string host) => _suspended.Any(s => host == s || host.EndsWith("." + s))
+				? new DomainBlock { Domain = host, Severity = DomainBlockSeverity.Suspend }
+				: default;
+			public bool IsSuspended(string host) => Find(host) != default;
+			public Task Reload(CancellationToken token) => Task.CompletedTask;
+		}
+
 		sealed class StaticOptionsMonitor : IOptionsMonitor<FederationOptions>
 		{
 			public StaticOptionsMonitor(FederationOptions value) => CurrentValue = value;