feat: identify, presence update commands

Foxcord/Gateway/Events/Commands/HeartbeatCommand.cs

@@ -0,0 +1,13 @@
+namespace Foxcord.Gateway.Events.Commands;
+
+public record HeartbeatCommand(long? Sequence) : IGatewayCommand
+{
+    public GatewayPacket ToGatewayPacket()
+    {
+        return new GatewayPacket
+        {
+            Opcode = GatewayOpcode.Heartbeat,
+            Payload = Sequence
+        };
+    }
+}

Foxcord/Gateway/Events/Commands/IGatewayCommand.cs

@@ -0,0 +1,6 @@
+namespace Foxcord.Gateway.Events.Commands;
+
+public interface IGatewayCommand
+{
+    public GatewayPacket ToGatewayPacket();
+}

Foxcord/Gateway/Events/Commands/PresenceUpdateCommand.cs

@@ -0,0 +1,46 @@
+using Foxcord.Models;
+
+namespace Foxcord.Gateway.Events.Commands;
+
+public class PresenceUpdateCommand : IGatewayCommand
+{
+    public long? Since { get; init; }
+    public Activity[] Activities { get; init; } = [];
+    public PresenceStatusType Status { get; init; }
+    public bool Afk { get; init; }
+
+    public GatewayPacket ToGatewayPacket()
+    {
+        return new GatewayPacket
+        {
+            Opcode = GatewayOpcode.PresenceUpdate,
+            Payload = ToPayload()
+        };
+    }
+
+    public PresenceUpdatePayload ToPayload()
+    {
+        var status = Status switch
+        {
+            PresenceStatusType.Online => "online",
+            PresenceStatusType.Dnd => "dnd",
+            PresenceStatusType.Idle => "idle",
+            PresenceStatusType.Invisible => "invisible",
+            PresenceStatusType.Offline => "offline",
+            _ => throw new ArgumentOutOfRangeException()
+        };
+        
+        return new PresenceUpdatePayload(Since, Activities, status, Afk);
+    }
+
+    public record PresenceUpdatePayload(long? Since, Activity[] Activities, string Status, bool Afk);
+}
+
+public enum PresenceStatusType
+{
+    Online,
+    Dnd,
+    Idle,
+    Invisible,
+    Offline
+}

Foxcord/Gateway/Events/IdentifyEvent.cs

@@ -1,3 +1,6 @@
+using System.Text.Json.Serialization;
+using Foxcord.Gateway.Events.Commands;
+
 namespace Foxcord.Gateway.Events;
 
 public class IdentifyEvent : IGatewayEvent
@@ -5,6 +8,10 @@ public class IdentifyEvent : IGatewayEvent
     public required string Token { get; init; }
     public IdentifyProperties Properties { get; init; } = new();
     public GatewayIntent Intents { get; init; }
+    public PresenceUpdateCommand.PresenceUpdatePayload? Presence { get; init; }
+
+    [JsonIgnore(Condition = JsonIgnoreCondition.WhenWritingNull)]
+    public int[]? Shards { get; init; }
 }
 
 public class IdentifyProperties