Сообщения в ПДА (#564)

* add: Сообщения в ПДА

* Search bar and colors in messages on the PDA

Content.Shared/_White/CartridgeLoader/Cartridges/MessagesUiState.cs

@@ -0,0 +1,47 @@
+using Robust.Shared.Serialization;
+
+namespace Content.Shared._White.CartridgeLoader.Cartridges;
+
+///<summary>
+/// The state of the messages app interface.
+/// Mode switches whether the UI should display a list of other users or a particular chat.
+/// Contents contains either the names of users and their ids in the messages system or simply a list of message strings.
+///</summary>
+[Serializable, NetSerializable]
+public sealed class MessagesUiState(MessagesUiStateMode mode, List<(MessagesUser, int?)> contents, string? name = null) : BoundUserInterfaceState
+{
+    public List<(MessagesUser, int?)>? Contents = contents;
+    public MessagesUiStateMode Mode = mode;
+    public string? Name = name;
+}
+
+///<summary>
+/// Enum representing the modes the program's UI can be in
+///</summary>
+[Serializable, NetSerializable]
+public enum MessagesUiStateMode : byte
+{
+    UserList,
+    Chat,
+    Error
+}
+
+///<summary>
+/// Data of a single message in the system, containing the ids of the sender and recipient, the text content and the time it was sent.
+///</summary>
+[Serializable, NetSerializable]
+public struct MessagesMessageData
+{
+    public int SenderId;
+    public int ReceiverId;
+    public string Content;
+    public TimeSpan Time;
+}
+
+[Serializable]
+public sealed class MessagesUser(string name, string job, string department)
+{
+    public string Name = name;
+    public string Job = job;
+    public string Department = department;
+}