refactor!: Use Func<Task> for scheduled tasks

Entities/ScheduledTask.cs

@@ -0,0 +1,35 @@
+namespace Xorog.UniversalExtensions.Entities;
+
+public class ScheduledTask
+{
+    internal ScheduledTask()
+    {
+        this.Uid = Guid.NewGuid().ToString();
+    }
+
+    /// <summary>
+    /// The unique identifier of this task.
+    /// </summary>
+    public string Uid { get; internal set; }
+
+    /// <summary>
+    /// The custom data asscociated with this task.
+    /// </summary>
+    public object? CustomData { get; internal set; }
+
+    /// <summary>
+    /// The time this task will run.
+    /// </summary>
+    public DateTime? RunTime { get; internal set; }
+
+    /// <summary>
+    /// The <see cref="CancellationTokenSource"/> to prematurely dequeue this task.
+    /// </summary>
+    internal CancellationTokenSource? TokenSource { get; set; } = new();
+
+    /// <summary>
+    /// Delete this task.
+    /// </summary>
+    public void Delete() =>
+        ScheduledTaskExtensions.DeleteScheduledTask(Uid);
+}