Add reference field

maquila.py

@@ -138,6 +138,7 @@ class Contract(sequence_ordered(), Workflow, ModelSQL, ModelView):
             },
         depends=['state'])
     number = fields.Char('Number', readonly=True, select=True)
+    reference = fields.Char('Reference')
     party = fields.Many2One('party.party', "Party", required=True,
         states={
             'readonly': Eval('state') != 'draft',

view/maquila_contract_form.xml

@@ -1,11 +1,13 @@
 <?xml version="1.0"?>
 <form>
+  <label name="number"/>
+  <field name="number"/>
+  <label name="reference"/>
+  <field name="reference"/>
   <label name="party"/>
   <field name="party"/>
   <label name="product"/>
   <field name="product"/>
-  <label name="number"/>
-  <field name="number"/>
   <label name="company"/>
   <field name="company"/>
   <label name="quantity"/>