P6: quote posts, received and sent (FEP-044f and the older keys)

- Received quotes: read from `quote`, `quoteUrl`, `quoteUri`, `_misskey_quote` or a FEP-e232 Link tag; the quoted post
  is fetched once; a quoteAuthorization stamp is verified field by field on the quoted author's origin; a consent
  quote without a stamp is pending; an older-key quote of a public post is shown; Delete of a stamp revokes. Counts
  and a `quote` notification follow the accepted state. The `quote-inline` fallback survives sanitising and is removed
  from content when the real quote is shown.
- Personas quote through `quoted_status_id`: posts that state a quote policy get a QuoteRequest and stay pending until
  an Accept brings a stamp we can verify, then an Update adds quoteAuthorization; posts that state none are quoted
  the older way, without `quote`; another persona's posts cannot be quoted yet (we issue no stamps). Quoting posts
  are delivered to the quoted author too.
- Mastodon API: Status.quote (with the quoted status one level deep), quotes_count, quote_approval from the remote
  policy, GET /api/v1/statuses/:id/quotes, `quote` notifications, and api_versions.mastodon = 7.

Checked live: GoToSocial's author-only quote policy is respected.

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

PrivaPub/Domain/Statuses/StatusService.cs

@@ -40,6 +40,7 @@ namespace PrivaPub.Domain.Statuses
 		public double? Longitude { get; init; }
 		public double? RangeKm { get; init; }
 		public PollDraft Poll { get; init; }
+		public string QuotedStatusId { get; init; }
 	}
 
 	public sealed record StatusOutcome(PostEntity Post, int Status = StatusCodes.Status200OK, string Error = default)
@@ -72,12 +73,14 @@ namespace PrivaPub.Domain.Statuses
 		readonly IGroupDistributor _groups;
 		readonly IPollService _polls;
 		readonly ILinkPreviews _previews;
+		readonly IQuoteService _quotes;
 
 		public StatusService(DbEntities dbEntities, ILocalActorService localActors, IRemoteActorService remoteActors, IDeliveryService delivery,
 			IContentRenderer content, IOutboxPublisher outbox, IFanout fanout, IMediaService media, IGroupDistributor groups, IPollService polls,
-			ILinkPreviews previews)
+			ILinkPreviews previews, IQuoteService quotes)
 		{
 			_previews = previews;
+			_quotes = quotes;
 			_polls = polls;
 			_media = media;
 			_groups = groups;
@@ -115,6 +118,18 @@ namespace PrivaPub.Domain.Statuses
 			if (parent != default && !await VisibilityPolicy.CanSee(parent, author.Id, token))
 				return StatusOutcome.Fail(StatusCodes.Status404NotFound, "Record not found");
 
+			PostEntity quoted = default;
+			var quotePermission = QuotePermission.Denied;
+			if (!string.IsNullOrEmpty(draft.QuotedStatusId))
+			{
+				quoted = await _dbEntities.Posts.Match(p => p.ID == draft.QuotedStatusId && !p.DeletedAt.HasValue && p.ReblogOfPostId == null).ExecuteFirstAsync(token);
+				if (quoted == default || !await VisibilityPolicy.CanSee(quoted, author.Id, token))
+					return StatusOutcome.Fail(StatusCodes.Status404NotFound, "Record not found");
+				quotePermission = _quotes.Permission(quoted, author);
+				if (quotePermission == QuotePermission.Denied)
+					return StatusOutcome.Fail(StatusCodes.Status422UnprocessableEntity, "Validation failed: This post cannot be quoted");
+			}
+
 			var located = draft.Latitude.HasValue || draft.Longitude.HasValue;
 			if (located && (draft.Latitude is not (>= -90 and <= 90) || draft.Longitude is not (>= -180 and <= 180) || group != default
 				|| draft.Visibility == PostVisibility.Direct))
@@ -166,7 +181,11 @@ namespace PrivaPub.Domain.Statuses
 				InReplyToAccountId = parent?.AuthorAccountId ?? parent?.GroupUserId,
 				IsLocalOnly = isLocalOnly,
 				ActorURI = author.Uri,
-				Poll = draft.Poll == default ? default : _polls.Create(draft.Poll)
+				Poll = draft.Poll == default ? default : _polls.Create(draft.Poll),
+				QuoteURI = quoted?.ObjectURI,
+				QuotedPostId = quoted?.ID,
+				QuoteByConsent = quoted != default && (quoted.QuotePolicy != default || !quoted.IsFederatedCopy),
+				QuoteState = quoted == default ? QuoteState.None : quotePermission == QuotePermission.Granted ? QuoteState.Accepted : QuoteState.Pending
 			};
 			post.ID = (string)post.GenerateNewID();
 			post.ObjectURI = author.PostUri(post.ID);
@@ -210,6 +229,10 @@ namespace PrivaPub.Domain.Statuses
 				await DB.Default.Update<PostEntity>().MatchID(parent.ID).Modify(b => b.Inc(p => p.RepliesCount, 1)).ExecuteAsync(token);
 			await _fanout.Distribute(post, token);
 			await _polls.Scheduled(post, token);
+			if (post.QuoteState == QuoteState.Accepted)
+				await DB.Default.Update<PostEntity>().MatchID(quoted.ID).Modify(b => b.Inc(p => p.QuotesCount, 1)).ExecuteAsync(token);
+			if (post.QuoteState == QuoteState.Pending && create?["object"] is JsonObject quotingNote)
+				await _quotes.Request(author, post, quoted, quotingNote, token);
 			await _previews.Wanted(post, token);
 			if (create != default)
 				await _outbox.Publish(author, post, create, token);