The statistics name RFC 9421 signatures

A delivery signed with RFC 9421 was counted under "other": its algorithm
(rsa-v1_5-sha256) has an underscore, which a signature name could not
hold. It is now counted as rfc9421:rsa-v1_5-sha256, as WordPress's are.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LsXgEaXee4GCU1hwYgPJXw

PrivaPub.Tests/Statistics/InteractionsTests.cs

@@ -49,6 +49,8 @@ namespace PrivaPub.Tests.Statistics
 			Assert.Equal("-", Interactions.Host("evil host/with path"));
 			Assert.Equal("-", Interactions.Host(default));
 			Assert.Equal("social.example", Interactions.HostOf("https://Social.Example:8443/users/x"));
+			// RFC 9421's algorithm names carry an underscore
+			Assert.Equal("rfc9421:rsa-v1_5-sha256", Interactions.Sanitize(new InteractionEvent { Signature = "rfc9421:rsa-v1_5-sha256" }).Signature);
 		}
 
 		[Fact]

PrivaPub/Infrastructure/Statistics/Interactions.cs

@@ -95,7 +95,7 @@ namespace PrivaPub.Infrastructure.Statistics
 		[GeneratedRegex("^[a-z0-9][a-z0-9-]{0,39}$")]
 		private static partial Regex KebabWord();
 
-		[GeneratedRegex("^[a-z0-9][a-z0-9:-]{0,39}$")]
+		[GeneratedRegex("^[a-z0-9][a-z0-9:_-]{0,39}$")]
 		private static partial Regex SignatureName();
 
 		[GeneratedRegex("^[a-z0-9][a-z0-9:/+.-]{0,63}$")]