Scheduled event update bugfixes (#81)

This PR fixes the following bugs in ScheduledEventUpdateService:
- When a scheduled event is first added into ScheduledEventData, its
status update code will be skipped. This results in some messages not
being sent to the EventNotificationChannel
- When the status update code returns an unsuccessful Result, the status
in ScheduledEventData will still be updated, meaning that the code will
not retry.

---------

Signed-off-by: Octol1ttle <l1ttleofficial@outlook.com>

src/Data/ScheduledEventData.cs

@@ -8,12 +8,12 @@ namespace Boyfriend.Data;
 /// <remarks>This information is stored on disk as a JSON file.</remarks>
 public sealed class ScheduledEventData
 {
-    public ScheduledEventData(GuildScheduledEventStatus status)
+    public ScheduledEventData(GuildScheduledEventStatus? status)
     {
         Status = status;
     }
 
     public bool EarlyNotificationSent { get; set; }
     public DateTimeOffset? ActualStartTime { get; set; }
-    public GuildScheduledEventStatus Status { get; set; }
+    public GuildScheduledEventStatus? Status { get; set; }
 }