add _ to password regex

config/application.rb

@@ -67,7 +67,7 @@ module Osuny
       "sgid", "content-type", "url", "filename", "filesize", "previewable"
     ]
 
-    config.allowed_special_chars = '#?!,@$%^&*+:;£µ-'
+    config.allowed_special_chars = '#?!,_@$%^&*+:;£µ-'
 
     config.generators do |g|
       g.orm :active_record, primary_key_type: :uuid