Avoid deleting messages from the store if they're not webhooks

PluralKit.Bot/Bot.cs

@@ -80,7 +80,7 @@ namespace PluralKit.Bot
 
             .AddSingleton<IDiscordClient, DiscordShardedClient>(_ => new DiscordShardedClient(new DiscordSocketConfig
             {
-                MessageCacheSize = 0,
+                MessageCacheSize = 10,
                 ExclusiveBulkDelete = true
             }))
             .AddSingleton<Bot>()

PluralKit.Bot/Services/ProxyService.cs

@@ -273,6 +273,10 @@ namespace PluralKit.Bot
 
         public async Task HandleMessageDeletedAsync(Cacheable<IMessage, ulong> message, ISocketMessageChannel channel)
         {
+            // Don't delete messages from the store if they aren't webhooks
+            // Non-webhook messages will never be stored anyway.
+            // If we're not sure (eg. message outside of cache), delete just to be sure.
+            if (message.HasValue && !message.Value.Author.IsWebhook) return;
             await _messageStorage.Delete(message.Id);
         }