Auto-pruning of syncshell, added metrics for pruning, return of count of users in fullgroupdto.

LightlessSyncServer/LightlessSyncShared/Models/Group.cs

@@ -12,6 +12,8 @@ public class Group
     [MaxLength(50)]
     public string Alias { get; set; }
     public GroupProfile? Profile { get; set; }
+    public bool AutoPruneEnabled { get; set; } = false;
+    public int AutoPruneDays { get; set; } = 0;
     public bool InvitesEnabled { get; set; }
     public string HashedPassword { get; set; }
     public bool PreferDisableSounds { get; set; }