feat: @silent support

Discord [relatively] recently added support for supressing notifications by typing @silent before the message content. This applies 1 << 12 to the message flags, and does not emit a notification, but still shows the highlight/mention in the channel you've been mentioned in.

Up until now, this bot did not support this functionality, neither in the sense of utilizing the feature or respecting messages attributed with 1 << 12.

This commit is the main purpose of the subsequent PR this will be in, allowing for users to quietly mention users in a channel, effectively bringing the bot in parity with the original message in that sense as well.

src/Events/MessageCreatedEventHandler.cs

@@ -16,6 +16,7 @@ public sealed partial class MessageCreatedEventHandler
 
     public static async Task ExecuteAsync(DiscordClient _, MessageCreateEventArgs eventArgs)
     {
+        bool shouldSilence = eventArgs.Message.Flags is { } flags && flags.HasFlag(MessageFlags.SupressNotifications);
         DiscordMessage message = eventArgs.Message;
         // Explicitly cast to nullable to prevent erroneous compiler warning about it
         // not being nullable.
@@ -32,6 +33,7 @@ public static async Task ExecuteAsync(DiscordClient _, MessageCreateEventArgs ev
         {
             mentionedUsers = mentionedUsers.Prepend(eventArgs.Message.ReferencedMessage.Author);
         }
+
 
         // Only mention the users that the message intended to mention.
         foreach (DiscordUser user in mentionedUsers)
@@ -69,7 +71,15 @@ public static async Task ExecuteAsync(DiscordClient _, MessageCreateEventArgs ev
 
             try
             {
-                await member.SendMessageAsync($"You were pinged in {eventArgs.Channel.Mention} by {message.Author.Mention}: {message.JumpLink}");
+                var builder = new DiscordMessageBuilder()
+                    .WithContent($"You were pinged by {message.Author.Mention} in {eventArgs.Channel.Mention}. [Jump! \u2197]({message.JumpLink})");
+
+                if (shouldSilence)
+                {
+                    builder.SuppressNotifications();
+                }
+
+                await member.SendMessageAsync(builder);
             }
             catch (DiscordException error)
             {