Adds DSay command (#2901)

* DSay command

* Moves getting the clients from DeadChat and AdminDeadChat to a function

Content.Server/Administration/Commands/DSay.cs

@@ -0,0 +1,40 @@
+using Content.Server.Interfaces.Chat;
+using Content.Shared.Administration;
+using Robust.Server.Interfaces.Console;
+using Robust.Server.Interfaces.Player;
+using Robust.Shared.IoC;
+using Robust.Shared.Localization;
+
+namespace Content.Server.Administration.Commands
+{
+    [AdminCommand(AdminFlags.Admin)]
+    class DSay : IClientCommand
+    {
+        public string Command => "dsay";
+
+        public string Description => Loc.GetString("Sends a message to deadchat as an admin");
+
+        public string Help => Loc.GetString($"Usage: {Command} <message>");
+
+        public void Execute(IConsoleShell shell, IPlayerSession player, string[] args)
+        {
+            if (player == null)
+            {
+                shell.SendText((IPlayerSession) null, "Only players can use this command");
+                return;
+            }
+
+            if (args.Length < 1)
+                return;
+
+            var message = string.Join(" ", args).Trim();
+            if (string.IsNullOrEmpty(message))
+                return;
+
+            var chat = IoCManager.Resolve<IChatManager>();
+
+            chat.SendAdminDeadChat(player, message);
+            
+        }
+    }
+}