feat: flesh out member remove responder

Catalogger.Backend/Extensions/DiscordExtensions.cs

@@ -81,6 +81,20 @@ public static class DiscordExtensions
         if (!ctx.TryGetGuildID(out var guildId)) throw new CataloggerError("No guild ID in context");
         return (userId, guildId);
     }
+    
+    /// <summary>
+    /// Sorts a list of roles by their position in the Discord interface.
+    /// </summary>
+    /// <param name="roles">The list of guild roles to filter.</param>
+    /// <param name="filterByIds">An optional list of role IDs to return, from a member object or similar.
+    /// If null, the entire list is returned.</param>
+    /// <returns></returns>
+    public static IEnumerable<IRole> Sorted(this IEnumerable<IRole> roles,
+        IEnumerable<Snowflake>? filterByIds = null)
+    {
+        var sorted = roles.OrderByDescending(r => r.Position);
+        return filterByIds != null ? sorted.Where(r => filterByIds.Contains(r.ID)) : sorted;
+    }
 
     public class DiscordRestException(string message) : Exception(message);
 }