M6: provenance fixes, stored features, community edits that are real edits

- A fetched ObjectRecord no longer wears the signature, key, signed headers and @context
  of the activity that caused the fetch, and its ReceivedAt is the fetch's own time. Its
  activity fields now name the trigger. Provenance answers signature null and
  fetchedBy "instance-actor". Migration _008 clears the old fetched records.
- ObjectRecords store their ObjectFeatures extensions and context namespaces (migration
  _009 fills older records in batches), so statistics can count them. Provenance reads the
  stored lists.
- ForeignAvatar.Features records what an actor document uses (ActorFeatures): featured,
  shared inbox, FEP-521a, FEP-8b32, identity proofs, Misskey fields, indexable,
  undiscoverable, locked, key size, and more.
- RemoteEdits.Apply and RemoteDeletes.Remove are shared by the Update, Delete and Announce
  handlers. A community-wrapped Update is now an edit only when newer, refreshes polls
  and media otherwise, revises the ObjectRecord and re-resolves quotes. A
  community-wrapped Delete now tombstones the object, removes its ObjectRecord, reblogs
  and timeline rows, and lowers the reply count. Any deleted quoting post lowers the
  quoted post's quote count.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01ELjqpznMFMNrJoJUj6K5p2

PrivaPub/Federation/Inbox/RemoteEdits.cs

@@ -0,0 +1,106 @@
+using MongoDB.Entities;
+
+using PrivaPub.Domain.Statuses;
+using PrivaPub.Federation.Actors;
+using PrivaPub.Federation.Objects;
+using PrivaPub.Models.Federation;
+using PrivaPub.Models.Post;
+using PrivaPub.Models.Social;
+
+using PostEntity = PrivaPub.Models.Post.Post;
+
+namespace PrivaPub.Federation.Inbox
+{
+	public static class RemoteEdits
+	{
+		public const int MaxRevisions = 20;
+
+		public static bool IsEdit(NoteDocument note, PostEntity post) =>
+			note.Updated is { } updated && updated > (post.EditedAt ?? post.CreationDate);
+
+		public static async Task<bool> Apply(PostEntity post, NoteDocument note, string activityId, ILocalActorService localActors, IObjectRecords records,
+			IQuoteService quotes, CancellationToken token)
+		{
+			post.Poll = note.Poll ?? post.Poll;
+			post.QuotePolicy = note.QuotePolicy;
+			post.Video = note.Video ?? post.Video;
+			post.Audio = note.Audio ?? post.Audio;
+			post.Event = note.Event ?? post.Event;
+			if (!IsEdit(note, post))
+			{
+				await DB.Default.SaveAsync(post, token);
+				await records.Revise(note, activityId, token);
+				await Requote(post, note, quotes, token);
+				return false;
+			}
+
+			post.Revisions.Add(new PostRevision
+			{
+				Title = post.Title,
+				SpoilerText = post.SpoilerText,
+				ContentHtml = post.ContentHtml,
+				HasContentWarning = post.HasContentWarning,
+				EditedAt = post.EditedAt ?? post.CreationDate
+			});
+			if (post.Revisions.Count > MaxRevisions)
+				post.Revisions.RemoveRange(0, post.Revisions.Count - MaxRevisions);
+
+			var mentions = new List<PostMention>();
+			foreach (var mention in note.Mentions)
+			{
+				var local = await localActors.FindByUri(mention.ActorURI, token);
+				mentions.Add(new PostMention { ActorURI = mention.ActorURI, Handle = mention.Handle, IsLocal = local != default, AccountId = local?.Id });
+			}
+
+			post.Title = note.Title;
+			post.SpoilerText = note.SpoilerText;
+			post.Excerpt = note.Excerpt;
+			post.Source = note.Source;
+			post.Emojis = note.Emojis.ToList();
+			post.CoverURL = note.CoverURL;
+			post.Link = note.Link;
+			post.HasContentWarning = note.Sensitive;
+			post.Text = note.ContentHtml;
+			post.ContentHtml = note.ContentHtml;
+			post.Language = note.Language;
+			post.Tags = note.Tags.ToList();
+			post.Mentions = mentions;
+			post.Media = note.Attachments.ToList();
+			post.EditedAt = note.Updated ?? DateTime.UtcNow;
+			post.UpdateDate = DateTime.UtcNow;
+			await DB.Default.SaveAsync(post, token);
+			await records.Revise(note, activityId, token);
+			await Requote(post, note, quotes, token);
+			return true;
+		}
+
+		static async Task Requote(PostEntity post, NoteDocument note, IQuoteService quotes, CancellationToken token)
+		{
+			if (note.QuoteUri != post.QuoteURI || note.QuoteAuthorization != post.QuoteAuthorizationURI || post.QuoteState != QuoteState.Accepted)
+				await quotes.Resolve(post, note, token);
+		}
+	}
+
+	public static class RemoteDeletes
+	{
+		public static async Task Tombstone(string objectUri, CancellationToken token) =>
+			await DB.Default.Update<DeletedObject>()
+				.Match(d => d.ObjectURI == objectUri)
+				.Modify(d => d.DeletedAt, DateTime.UtcNow)
+				.Option(o => o.IsUpsert = true)
+				.ExecuteAsync(token);
+
+		public static async Task Remove(PostEntity post, string objectUri, CancellationToken token)
+		{
+			await Tombstone(objectUri, token);
+			await DB.Default.DeleteAsync<PostEntity>(post.ID);
+			await DB.Default.DeleteAsync<ObjectRecord>(r => r.PostId == post.ID || r.ObjectURI == objectUri);
+			await DB.Default.DeleteAsync<TimelineEntry>(e => e.PostId == post.ID || e.ReblogOfPostId == post.ID);
+			await DB.Default.DeleteAsync<PostEntity>(p => p.ReblogOfPostId == post.ID);
+			if (!string.IsNullOrEmpty(post.AnsweringToPostId))
+				await DB.Default.Update<PostEntity>().MatchID(post.AnsweringToPostId).Modify(b => b.Inc(p => p.RepliesCount, -1)).ExecuteAsync(token);
+			if (post.QuoteState == QuoteState.Accepted && !string.IsNullOrEmpty(post.QuotedPostId))
+				await DB.Default.Update<PostEntity>().MatchID(post.QuotedPostId).Modify(b => b.Inc(p => p.QuotesCount, -1)).ExecuteAsync(token);
+		}
+	}
+}