A remote account's Block of a persona is enforced

Inbound Block was dropped as an unknown type (the pasture's last
Mastodon expected failure, G-0002). Now, as Mastodon does it: the
follows between the blocker and the persona end here too (nothing is
sent back; the blocker already ended its side), the blocker's posts and
notifications are hidden from the persona and kept out of its home, the
persona's posts are no longer addressed to the blocker by mention or
reply, and the relationship says blocked_by. Undo{Block} lifts it. The
block is kept in BlockedBy, unique per persona and blocker.

The Mastodon scenario checks blocked_by instead of expecting a failure.

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

PrivaPub/Domain/Relationships/RelationshipService.cs

@@ -179,6 +179,9 @@ namespace PrivaPub.Domain.Relationships
 			var now = DateTime.UtcNow;
 			foreach (var block in await DB.Default.Find<Block>().Match(b => b.AvatarId == avatarId && uris.Contains(b.TargetActorURI)).ExecuteAsync(token))
 				hidden.Add(block.TargetActorURI);
+			//an account that blocked the persona is hidden from it too, as Mastodon hides it from the blocked account's home
+			foreach (var blocker in await DB.Default.Find<BlockedBy>().Match(b => b.AvatarId == avatarId && uris.Contains(b.ActorURI)).ExecuteAsync(token))
+				hidden.Add(blocker.ActorURI);
 			foreach (var mute in await DB.Default.Find<Mute>().Match(m => m.AvatarId == avatarId && uris.Contains(m.TargetActorURI)).ExecuteAsync(token))
 				if ((mute.ExpiresAt == null || mute.ExpiresAt > now) && (!forNotifications || mute.HideNotifications))
 					hidden.Add(mute.TargetActorURI);
@@ -198,6 +201,8 @@ namespace PrivaPub.Domain.Relationships
 			var now = DateTime.UtcNow;
 			foreach (var block in await DB.Default.Find<Block>().Match(b => ids.Contains(b.AvatarId) && b.TargetActorURI == actorUri).ExecuteAsync(token))
 				hiding.Add(block.AvatarId);
+			foreach (var blocked in await DB.Default.Find<BlockedBy>().Match(b => ids.Contains(b.AvatarId) && b.ActorURI == actorUri).ExecuteAsync(token))
+				hiding.Add(blocked.AvatarId);
 			foreach (var mute in await DB.Default.Find<Mute>().Match(m => ids.Contains(m.AvatarId) && m.TargetActorURI == actorUri).ExecuteAsync(token))
 				if (mute.ExpiresAt == null || mute.ExpiresAt > now)
 					hiding.Add(mute.AvatarId);