Import december-2020-12-18 from private repo (scrubbed 2026-05-27)

Targets Rec Room 2020.12.18 client.

Re-import after adding:
- DorkNet.ClientMod/dorknet-clientmod.json.template — config schema
  the launcher's manifest-driven patcher renders into UserData/.
- tools/build-patcher-zip.ps1 — produces the dorknet-clientpatch-{key}.zip
  Release asset the launcher fetches.
- .github/workflows/release.yml — auto-publishes both Release assets
  on v1-december-* tag push.

Scrubbed via maintainer-side scrub-for-public.ps1: same drop rules as
the prior import, plus build-patcher-zip.ps1 added to the tools/
allow-list so it survives the scrub.

DorkNet.Server/Data/Entities/MessageEntity.cs

@@ -0,0 +1,42 @@
+using System.ComponentModel.DataAnnotations;
+
+namespace DorkNet.Server.Data.Entities;
+
+/// <summary>
+/// Direct message between two players. Backs the watch's
+/// <c>api/messages/v2</c> endpoints (inbox + send + mark-read).
+///
+/// One row per message. Threading happens at read time — the inbox
+/// query groups by (Sender, Recipient) pair to surface the most
+/// recent message per conversation.
+/// </summary>
+public class MessageEntity
+{
+    public long Id { get; set; }
+
+    public long SenderPlayerId { get; set; }
+    public long RecipientPlayerId { get; set; }
+
+    [MaxLength(2000)]
+    public string Body { get; set; } = string.Empty;
+
+    /// <summary>RecNet <c>Message.MessageType</c> wire value (see
+    /// <c>Cpp2IL_CS/.../RecNet/Message.cs</c>). Default 30 =
+    /// TextMessage. Other values used by the 2020 client: 0/6 =
+    /// GameInvite[V2], 3/7 = PartyActivitySwitch[V2], 10 =
+    /// RequestGameInvite (the "ask to join" flow), 1 =
+    /// GameInviteDeclined, 11 = RequestGameInviteDeclined, 20 =
+    /// FriendStatusOnline.</summary>
+    public int Type { get; set; } = 30;
+
+    /// <summary>Optional RecNet room id carried by invite and party
+    /// activity messages. The client uses this to render room-aware
+    /// cards and passes it back when accepting V2 invites.</summary>
+    public long? RoomId { get; set; }
+
+    public DateTime SentAt { get; set; } = DateTime.UtcNow;
+
+    /// <summary>Null until the recipient hits the message in the
+    /// watch UI; set to the read timestamp at that point.</summary>
+    public DateTime? ReadAt { get; set; }
+}