Blocks, mutes, bookmarks, pins and reports

- Blocks are per persona and never federate (a Block activity would tell
  the other server who blocked whom): the blocked account is removed as a
  follower, with a Reject{Follow} if it is remote, unfollowed, cleared from
  home and notifications, and refused with Reject if it follows again.
- Mutes (optionally timed, optionally sparing notifications) and per-
  persona domain blocks keep authors out of home timelines, notifications
  and every status list the API returns; the boosts of a hidden author's
  posts are hidden too.
- Bookmarks and pins (at most five, public or unlisted, own posts) with
  their Mastodon endpoints and flags; pinned posts are the actor's
  `featured` collection at /trophies, and `featuredTags` points at
  /tattoos.
- Reports: /api/v1/reports stores the report and, when forwarding to a
  remote account, sends Flag from the instance actor, so the reporting
  persona is never named to the other server. An inbound Flag about a local
  persona or its posts becomes a report; moderators list and resolve them
  under /clientapi/moderator/reports.

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

PrivaPub/Api/Mastodon/Controllers/ReportsController.cs

@@ -0,0 +1,42 @@
+using Microsoft.AspNetCore.Mvc;
+
+using PrivaPub.Api.Mastodon.Infrastructure;
+using PrivaPub.Api.Mastodon.Mappers;
+using PrivaPub.Domain.Relationships;
+
+namespace PrivaPub.Api.Mastodon.Controllers
+{
+	public class ReportsController : MastodonController
+	{
+		readonly IReportService _reports;
+		readonly MastodonMapper _mapper;
+
+		public ReportsController(IReportService reports, MastodonMapper mapper)
+		{
+			_reports = reports;
+			_mapper = mapper;
+		}
+
+		[HttpPost("/api/v1/reports"), Scope("write:reports")]
+		public async Task<IActionResult> Create(CancellationToken token)
+		{
+			var report = await _reports.File(Me, Params.Get("account_id"), Params.List("status_ids"), Params.Get("comment"), Params.Get("category"),
+				Params.Bool("forward") == true, token);
+			if (report == default)
+				return NotFoundError();
+			return Json(new
+			{
+				id = report.ID,
+				action_taken = false,
+				action_taken_at = default(string),
+				category = report.Category,
+				comment = report.Comment ?? string.Empty,
+				forwarded = report.Forwarded,
+				created_at = MastodonJson.Time(report.CreatedAt),
+				status_ids = report.PostIds,
+				rule_ids = Array.Empty<string>(),
+				target_account = await _mapper.Account(report.TargetAccountId, token)
+			});
+		}
+	}
+}