[FIX] account: Bring back the 'Invoice' stat button on partner form

It has accidentally disappeared in saas-15.

addons/account/models/partner.py

@@ -1,5 +1,6 @@
 # -*- coding: utf-8 -*-
 
+from ast import literal_eval
 from operator import itemgetter
 import time
 
@@ -436,3 +437,11 @@ class ResPartner(models.Model):
         return super(ResPartner, self)._commercial_fields() + \
             ['debit_limit', 'property_account_payable_id', 'property_account_receivable_id', 'property_account_position_id',
              'property_payment_term_id', 'property_supplier_payment_term_id', 'last_time_entries_checked']
+
+    @api.multi
+    def action_view_partner_invoices(self):
+        self.ensure_one()
+        action = self.env.ref('account.action_invoice_refund_out_tree').read()[0]
+        action['domain'] = literal_eval(action['domain'])
+        action['domain'].append(('partner_id', 'child_of', self.id))
+        return action

addons/account/views/partner_view.xml

@@ -95,6 +95,17 @@
             <field name="priority" eval="20"/>
             <field name="groups_id" eval="[(4, ref('account.group_account_invoice'))]"/>
             <field name="arch" type="xml">
+                <div name="button_box" position="inside">
+                    <button type="object" class="oe_stat_button" icon="fa-pencil-square-o" name="action_view_partner_invoices"
+                        attrs="{'invisible': [('customer', '=', False)]}">
+                        <div class="o_form_field o_stat_info">
+                            <span class="o_stat_value">
+                                <field name="total_invoiced" widget='monetary' options="{'currency_field': 'currency_id'}"/>
+                            </span>
+                            <span class="o_stat_text">Invoiced</span>
+                        </div>
+                    </button>
+                </div>
                 <group name="container_row_2" position="inside">
                     <group string="Payments" name="banks">
                         <field name="currency_id" invisible="1"/>