[ADD] account check printing: 'Unmark Sent'

Possibility to go back from state 'sent' to 'posted'

addons/account_check_printing/account_payment.py

@@ -125,6 +125,10 @@ class account_payment(models.Model):
         else:
             return self.do_print_checks()
 
+    @api.multi
+    def unmark_sent(self):
+        self.write({'state': 'posted'})
+
     @api.multi
     def do_print_checks(self):
         """ This method is a hook for l10n_xx_check_printing modules to implement actual check printing capabilities """

addons/account_check_printing/views/account_payment_view.xml

@@ -7,7 +7,8 @@
             <field name="inherit_id" ref="account.view_account_payment_form" />
             <field name="arch" type="xml">
                 <xpath expr="//button[@name='post']" position="before">
-                    <button name="print_checks" class="oe_highlight" attrs="{'invisible': ['|', ('payment_method_code', '!=', 'check_printing'), ('state', 'not in', ('posted', 'sent'))]}" string="Print Check" type="object"/>
+                    <button name="print_checks" class="oe_highlight" attrs="{'invisible': ['|', ('payment_method_code', '!=', 'check_printing'), ('state', '!=', 'posted')]}" string="Print Check" type="object"/>
+                    <button name="unmark_sent" attrs="{'invisible': ['|', ('payment_method_code', '!=', 'check_printing'), ('state', '!=', 'sent')]}" string="Unmark Sent" type="object"/>
                 </xpath>
                 <xpath expr="//div[@name='amount_div']" position="after">
                     <field name="check_amount_in_words" attrs="{'invisible': [('payment_method_code', '!=', 'check_printing')], 'readonly': [('state', '!=', 'draft')]}" groups="base.group_no_one"/>