[FIX] point_of_sale: display cash balance on session

When you are opening the session form in the backend to display what has
been done during the session you cannot easily see what was the starting
and ending balance of the cash of a session.

So we are now displaying those fields in the session form.

closes odoo/odoo#102428

X-original-commit: 0ab780ec61d265e2d68d873bd8bc5b7bebfcd01f
Signed-off-by: Masereel Pierre <pim@odoo.com>

addons/point_of_sale/views/pos_session_view.xml

@@ -66,6 +66,8 @@
                         <field name="move_id" readonly="1" groups="account.group_account_readonly" />
                         <field name="start_at" attrs="{'invisible' : [('state', '=', 'opening_control')]}"/>
                         <field name="stop_at" attrs="{'invisible' : [('state', '!=', 'closed')]}"/>
+                        <field name="cash_register_balance_start"/>
+                        <field name="cash_register_balance_end_real" attrs="{'invisible': [('state', '!=', 'closed')]}"/>
                     </group>
                 </sheet>
                 <div class="oe_chatter">