feat: separate some Notification shared files.

src/Ursa/Controls/NotificationShared/IMessage.cs

@@ -0,0 +1,35 @@
+using Avalonia.Controls.Notifications;
+
+namespace Ursa.Controls;
+
+/// <summary>
+/// Represents a message that can be shown in a window or by the host operating system.
+/// </summary>
+public interface IMessage
+{
+    /// <summary>
+    /// Gets the <see cref="NotificationType"/> of the message.
+    /// </summary>
+    NotificationType Type { get; }
+
+    /// <summary>
+    /// Gets a value indicating whether the message should show a close button.
+    /// </summary>
+    bool ShowClose { get; }
+
+    /// <summary>
+    /// Gets the expiration time of the message after which it will automatically close.
+    /// If the value is <see cref="TimeSpan.Zero"/> then the message will remain open until the user closes it.
+    /// </summary>
+    TimeSpan Expiration { get; }
+
+    /// <summary>
+    /// Gets an Action to be run when the message is clicked.
+    /// </summary>
+    Action? OnClick { get; }
+
+    /// <summary>
+    /// Gets an Action to be run when the message is closed.
+    /// </summary>
+    Action? OnClose { get; }
+}