P5: downvotes, private messages from Lemmy, late Creates of deleted posts, and typed details for clients

- Dislike and its Undo are kept as downvotes (Lemmy, PieFed, Mbin, Friendica) and shown with favourites as votes.
- ChatMessage (Lemmy 0.19, Mbin, PieFed to those two) arrives as a direct message.
- A deleted object's id is remembered for 90 days, so a Create that arrives after its Delete cannot bring the post
  back; the post's ObjectRecord goes with it.
- A Join of one of our objects is answered with Ignore, as FEP-8a8e asks of a server without RSVP.
- A 503 with Retry-After is waited out like a 429 instead of counting as a failure of the host (GoToSocial throttling,
  Mastodon's temporary key failures).
- Status.privapub carries what a Mastodon Status cannot: object type, title, excerpt, cover, the author's source,
  link, video, audio and event details, and up/down votes, with every media URL proxied.

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

PrivaPub/Api/Mastodon/Entities/Entities.cs

@@ -49,6 +49,106 @@ namespace PrivaPub.Api.Mastodon.Entities
 		public string AttributionDomains { get; set; }
 	}
 
+	public class PrivaPubStatus
+	{
+		public string ObjectType { get; set; }
+		public string Title { get; set; }
+		public string Excerpt { get; set; }
+		public string Cover { get; set; }
+		public PrivaPubSource Source { get; set; }
+		public PrivaPubLink Link { get; set; }
+		public PrivaPubVideo Video { get; set; }
+		public PrivaPubAudio Audio { get; set; }
+		public PrivaPubEvent Event { get; set; }
+		public PrivaPubVotes Votes { get; set; } = new();
+	}
+
+	public class PrivaPubSource
+	{
+		public string Content { get; set; }
+		public string MediaType { get; set; }
+	}
+
+	public class PrivaPubLink
+	{
+		public string Url { get; set; }
+		public string Title { get; set; }
+		public string Description { get; set; }
+		public string Image { get; set; }
+		public bool FromPublisher { get; set; }
+	}
+
+	public class PrivaPubVariant
+	{
+		public string Url { get; set; }
+		public string MediaType { get; set; }
+		public int? Width { get; set; }
+		public int? Height { get; set; }
+		public double? Fps { get; set; }
+		public long? Size { get; set; }
+		public List<string> Streams { get; set; } = new();
+	}
+
+	public class PrivaPubVideo
+	{
+		public double? Duration { get; set; }
+		public List<PrivaPubVariant> Variants { get; set; } = new();
+		public bool IsLive { get; set; }
+		public int? State { get; set; }
+		public long? Views { get; set; }
+		public int? CommentsPolicy { get; set; }
+		public bool? DownloadEnabled { get; set; }
+		public string Licence { get; set; }
+		public string Category { get; set; }
+		public string Channel { get; set; }
+		public List<PrivaPubCaption> Captions { get; set; } = new();
+	}
+
+	public class PrivaPubCaption
+	{
+		public string Language { get; set; }
+		public string Url { get; set; }
+	}
+
+	public class PrivaPubAudio
+	{
+		public double? Duration { get; set; }
+		public List<PrivaPubVariant> Variants { get; set; } = new();
+		public string Album { get; set; }
+		public int? Position { get; set; }
+		public string Licence { get; set; }
+	}
+
+	public class PrivaPubEvent
+	{
+		public string Start { get; set; }
+		public string End { get; set; }
+		public string TimeZone { get; set; }
+		public bool Floating { get; set; }
+		public List<PrivaPubPlace> Places { get; set; } = new();
+		public string OnlineUrl { get; set; }
+		public string JoinMode { get; set; }
+		public int? Participants { get; set; }
+		public int? Capacity { get; set; }
+		public string Status { get; set; }
+		public string Category { get; set; }
+	}
+
+	public class PrivaPubPlace
+	{
+		public string Name { get; set; }
+		public string Address { get; set; }
+		public double? Latitude { get; set; }
+		public double? Longitude { get; set; }
+		public string Url { get; set; }
+	}
+
+	public class PrivaPubVotes
+	{
+		public int Up { get; set; }
+		public int Down { get; set; }
+	}
+
 	public class PreviewCard
 	{
 		public string Url { get; set; }
@@ -104,6 +204,7 @@ namespace PrivaPub.Api.Mastodon.Entities
 		public string Language { get; set; }
 		public string Text { get; set; }
 		public List<object> Filtered { get; set; } = new();
+		public PrivaPubStatus Privapub { get; set; }
 	}
 
 	public class MediaAttachment

PrivaPub/Api/Mastodon/Mappers/MastodonMapper.cs

@@ -194,6 +194,7 @@ namespace PrivaPub.Api.Mastodon.Mappers
 					Language = post.Language,
 					MediaAttachments = post.Media.Select(Media).ToList(),
 					Card = Card(post),
+					Privapub = Extension(post),
 					Mentions = post.Mentions.Select(m => Mention(m, mentionAccounts)).Where(m => m != default).ToList(),
 					Tags = post.Tags.Select(t => new StatusTag { Name = t, Url = ActivityPubRenderer.TagUrl(_localActors.BaseAddress, t) }).ToList()
 				};
@@ -269,6 +270,67 @@ namespace PrivaPub.Api.Mastodon.Mappers
 			}
 		}
 
+		PrivaPubStatus Extension(PostEntity post) => new()
+		{
+			ObjectType = post.ObjectType,
+			Title = post.IsFederatedCopy ? post.Title : default,
+			Excerpt = post.Excerpt,
+			Cover = Proxied(post.CoverURL),
+			Source = post.Source == default ? default : new PrivaPubSource { Content = post.Source.Content, MediaType = post.Source.MediaType },
+			Link = post.Link == default ? default : new PrivaPubLink
+			{
+				Url = post.Link.Href, Title = post.Link.Title, Description = post.Link.Description, Image = Proxied(post.Link.ImageURL), FromPublisher = post.Link.FromPublisher
+			},
+			Video = post.Video == default ? default : new PrivaPubVideo
+			{
+				Duration = post.Video.DurationSeconds,
+				Variants = post.Video.Variants.Select(Variant).ToList(),
+				IsLive = post.Video.IsLive,
+				State = post.Video.State,
+				Views = post.Video.Views,
+				CommentsPolicy = post.Video.CommentsPolicy,
+				DownloadEnabled = post.Video.DownloadEnabled,
+				Licence = post.Video.Licence,
+				Category = post.Video.Category,
+				Channel = post.Video.ChannelURI,
+				Captions = post.Video.Captions.Select(c => new PrivaPubCaption { Language = c.Language, Url = Proxied(c.Url) }).ToList()
+			},
+			Audio = post.Audio == default ? default : new PrivaPubAudio
+			{
+				Duration = post.Audio.DurationSeconds,
+				Variants = post.Audio.Variants.Select(Variant).ToList(),
+				Album = post.Audio.Album,
+				Position = post.Audio.Position,
+				Licence = post.Audio.Licence
+			},
+			Event = post.Event == default ? default : new PrivaPubEvent
+			{
+				Start = post.Event.Start is { } start ? MastodonJson.Time(start) : default,
+				End = post.Event.End is { } end ? MastodonJson.Time(end) : default,
+				TimeZone = post.Event.TimeZone,
+				Floating = post.Event.FloatingTime,
+				Places = post.Event.Places.Select(p => new PrivaPubPlace { Name = p.Name, Address = p.Address, Latitude = p.Latitude, Longitude = p.Longitude, Url = p.Url }).ToList(),
+				OnlineUrl = post.Event.OnlineURL,
+				JoinMode = post.Event.JoinMode,
+				Participants = post.Event.ParticipantCount,
+				Capacity = post.Event.Capacity,
+				Status = post.Event.Status,
+				Category = post.Event.Category
+			},
+			Votes = new PrivaPubVotes { Up = post.FavouritesCount, Down = post.DownvotesCount }
+		};
+
+		PrivaPubVariant Variant(MediaVariant variant) => new()
+		{
+			Url = Proxied(variant.Url),
+			MediaType = variant.MediaType,
+			Width = variant.Width,
+			Height = variant.Height,
+			Fps = variant.Fps,
+			Size = variant.Size,
+			Streams = variant.Streams
+		};
+
 		PreviewCard Card(PostEntity post)
 		{
 			if (!post.IsFederatedCopy)