add ATTACHMENT_SIZE_LIMIT, MAX_MESSAGE_SIZE, MAX_REACTION_SIZE & replace System.IO with custom Fs class

LarpixServer/Account/Requests.cs

@@ -885,7 +885,7 @@ public static async Task Auth(HttpContext context, Func<Task> next, IQueryCollec
             return;
         }
 
-        byte[] fileBytes = await LarpixServer.Utils.Utils.LoadBodyBytes(context.Request.Body, 50 * 1024 * 1024); // 50MB limit for attachments
+        byte[] fileBytes = await LoadBodyBytes(context.Request.Body, ATTACHMENT_SIZE_LIMIT); // attachment size limit
         if (fileBytes == null || fileBytes.Length == 0)
         {
             await context.Response.WriteAsync(Encryption.Encryption.EncryptString("error:empty.body", password));