Streaming: what happens, told as it happens

Mastodon's streaming API: /api/v1/streaming as a WebSocket (streams
subscribed in the URL or by message) and /api/v1/streaming/{stream} as
server-sent events, with health and the URL advertised. The user stream
tells posts reaching the persona's home (not those an exclusive list keeps
apart, which its list stream tells), notifications, edits and deletions;
public, hashtag and list streams tell what belongs in them. An in-process
hub carries ids only; each connection maps a post or a notification for its
own persona as it sends it, so nothing it may not see, or whose author it
blocked or muted, goes out. A deletion reaches only the streams that showed
the post. The token comes as access_token, header or WebSocket protocol.

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

PrivaPub/Api/Mastodon/Controllers/InstanceController.cs

@@ -40,6 +40,10 @@ namespace PrivaPub.Api.Mastodon.Controllers
 
 		string Domain => new Uri(_localActors.BaseAddress).Authority;
 
+		// where clients open their streams (StreamingController): this server, as ws or wss
+		string Streaming => new UriBuilder(_localActors.BaseAddress) { Scheme = _localActors.BaseAddress.StartsWith("https", StringComparison.OrdinalIgnoreCase) ? "wss" : "ws" }
+			.Uri.GetLeftPart(UriPartial.Authority);
+
 		// every limit is what the server enforces, read from where it is enforced
 		static object Statuses => new { max_characters = PrivaPub.Domain.Statuses.StatusService.MaxCharacters, max_media_attachments = 4, characters_reserved_per_url = 23 };
 
@@ -82,7 +86,7 @@ namespace PrivaPub.Api.Mastodon.Controllers
 				description = Description,
 				email = string.Empty,
 				version = Version,
-				urls = new { },//no streaming API yet, so none is advertised
+				urls = new { streaming_api = Streaming },
 				stats = new { user_count = users, status_count = statuses, domain_count = domains },
 				thumbnail = $"{_localActors.BaseAddress}/media/missing-header.png",
 				languages = LanguageCodes(HttpContext.RequestServices),
@@ -115,7 +119,7 @@ namespace PrivaPub.Api.Mastodon.Controllers
 			languages = LanguageCodes(HttpContext.RequestServices),
 			configuration = new
 			{
-				urls = new { },//no streaming API yet, so none is advertised
+				urls = new { streaming = Streaming },
 				accounts = new { max_featured_tags = 0, max_pinned_statuses = StatusesController.MaxPins },
 				statuses = Statuses,
 				media_attachments = MediaAttachments,