add gateway for admeme (#17587)

Co-authored-by: deltanedas <@deltanedas:kde.org>

Content.Server/Gateway/Components/GatewayComponent.cs

@@ -0,0 +1,40 @@
+using Content.Server.Gateway.Systems;
+using Robust.Shared.Audio;
+using Robust.Shared.Serialization.TypeSerializers.Implementations.Custom;
+
+namespace Content.Server.Gateway.Components;
+
+/// <summary>
+/// Controlling gateway that links to other gateway destinations on the server.
+/// </summary>
+[RegisterComponent, Access(typeof(GatewaySystem))]
+public sealed class GatewayComponent : Component
+{
+    /// <summary>
+    /// Sound to play when opening or closing the portal.
+    /// </summary>
+    [DataField("portalSound")]
+    public SoundSpecifier PortalSound = new SoundPathSpecifier("/Audio/Effects/Lightning/lightningbolt.ogg");
+
+    /// <summary>
+    /// Every other gateway destination on the server.
+    /// </summary>
+    /// <remarks>
+    /// Added on
+    /// </remarks>
+    [ViewVariables]
+    public HashSet<EntityUid> Destinations = new();
+
+    /// <summary>
+    /// The time at which the portal will be closed.
+    /// </summary>
+    [ViewVariables(VVAccess.ReadWrite), DataField("nextClose", customTypeSerializer:typeof(TimeOffsetSerializer))]
+    public TimeSpan NextClose;
+
+    /// <summary>
+    /// The time at which the portal was last opened.
+    /// Only used for UI.
+    /// </summary>
+    [ViewVariables]
+    public TimeSpan LastOpen;
+}