[FIX] lunch: remove required on user_id

* Since the user_id field is required, it was impossible to delete
  user when he had 'lunch.order' or 'lunch.cashmove'.
  We removed required arguments on 'user_id' fields in model and set
   "required='1'" on the fields in the view.
* There was a 'ondelete="cascade"' on 'order_line_ids' which does
  nothing because it's not supported on One2many fields.

addons/lunch/models/lunch.py

@@ -26,14 +26,14 @@ class LunchOrder(models.Model):
             for order in prev_order
         }.values()
 
-    user_id = fields.Many2one('res.users', 'User', required=True, readonly=True,
+    user_id = fields.Many2one('res.users', 'User', readonly=True,
                               states={'new': [('readonly', False)]},
                               default=lambda self: self.env.uid)
     date = fields.Date('Date', required=True, readonly=True,
                        states={'new': [('readonly', False)]},
                        default=fields.Date.context_today)
     order_line_ids = fields.One2many('lunch.order.line', 'order_id', 'Products',
-                                     ondelete="cascade", readonly=True, copy=True,
+                                     readonly=True, copy=True,
                                      states={'new': [('readonly', False)], False: [('readonly', False)]})
     total = fields.Float(compute='_compute_total', string="Total", store=True)
     state = fields.Selection([('new', 'New'),
@@ -220,7 +220,7 @@ class LunchCashMove(models.Model):
     _name = 'lunch.cashmove'
     _description = 'lunch cashmove'
 
-    user_id = fields.Many2one('res.users', 'User', required=True,
+    user_id = fields.Many2one('res.users', 'User',
                               default=lambda self: self.env.uid)
     date = fields.Date('Date', required=True, default=fields.Date.context_today)
     amount = fields.Float('Amount', required=True, help='Can be positive (payment) or negative (order or payment if user wants to get his money back)')

addons/lunch/views/lunch_views.xml

@@ -92,7 +92,7 @@
                 <form string="cashmove form">
                     <sheet>
                         <group>
-                            <field name="user_id"/>
+                            <field name="user_id" required="1"/>
                             <field name="date"/>
                             <field name="amount"/>
                         </group>
@@ -366,7 +366,7 @@
 
                         <group>
                             <group>
-                                <field name='user_id' class="oe_inline"/>
+                                <field name='user_id' class="oe_inline" required='1'/>
                                 <field name='date'/>
                             </group>
                             <div>