Add sales channels (#1103)

- [x] Data model
- [x] Enforce constraint
- [x] Filter order list
- [x] Set channel on created order
- [x] Products API
- [x] Order API
- [x] Tests
- [x] Filter reports
- [x] Resellers
- [ ] deploy plugins
  - [ ] posbackend
  - [ ] resellers
  - [ ] reports
- [x] Ticketlayouts
- [x] Support in pretixPOS

src/pretix/control/templates/pretixcontrol/item/index.html

@@ -26,6 +26,7 @@
                 </fieldset>
                 <fieldset>
                     <legend>{% trans "Availability" %}</legend>
+                    {% bootstrap_field form.sales_channels layout="control" %}
                     {% bootstrap_field form.available_from layout="control" %}
                     {% bootstrap_field form.available_until layout="control" %}
                     {% bootstrap_field form.max_per_order layout="control" %}

src/pretix/control/templates/pretixcontrol/order/index.html

@@ -114,6 +114,10 @@
                         <dd>{{ order.code }}</dd>
                         <dt>{% trans "Order date" %}</dt>
                         <dd>{{ order.datetime }}</dd>
+                        {% if sales_channel %}
+                            <dt>{% trans "Sales channel" %}</dt>
+                            <dd>{{ sales_channel.verbose_name }}</dd>
+                        {% endif %}
                         <dt>{% trans "Order locale" %}</dt>
                         <dd>
                             {{ display_locale }}