🚚 Rename activity in sphere to timeline

In order to leave the activity keyword for pass service user activity

DysonNetwork.Sphere/Timeline/TimelineDiscovery.cs

@@ -0,0 +1,26 @@
+using DysonNetwork.Shared.Models;
+using NodaTime;
+
+namespace DysonNetwork.Sphere.Timeline;
+
+public class TimelineDiscoveryEvent(List<DiscoveryItem> items) : ITimelineEvent
+{
+    public List<DiscoveryItem> Items { get; set; } = items;
+
+    public SnTimelineEvent ToActivity()
+    {
+        var now = SystemClock.Instance.GetCurrentInstant();
+        return new SnTimelineEvent
+        {
+            Id = Guid.NewGuid(),
+            Type = "discovery",
+            ResourceIdentifier = "discovery",
+            Data = this,
+            CreatedAt = now,
+            UpdatedAt = now,
+        };
+    }
+}
+
+public record DiscoveryItem(string Type, object Data);
+