Control: Add drag and drop to sort categories and products (#2242)

* add drag and drop to categories

* add drag and drop to products

* add light grey background to dragged element

* add missing th, add sr-only desc of columns

* group up/down/move elements

* improve visualizing drag-area by dimming others

* change up/down-links to buttons in form-post

* limit sorting to POST requests

Co-authored-by: Raphael Michel <michel@rami.io>

src/pretix/control/urls.py

@@ -239,6 +239,7 @@ urlpatterns = [
         re_path(r'^items/(?P<item>\d+)/$', item.ItemUpdateGeneral.as_view(), name='event.item'),
         re_path(r'^items/(?P<item>\d+)/up$', item.item_move_up, name='event.items.up'),
         re_path(r'^items/(?P<item>\d+)/down$', item.item_move_down, name='event.items.down'),
+        re_path(r'^items/reorder$', item.reorder_items, name='event.items.reorder'),
         re_path(r'^items/(?P<item>\d+)/delete$', item.ItemDelete.as_view(), name='event.items.delete'),
         re_path(r'^items/typeahead/meta/$', typeahead.item_meta_values, name='event.items.meta.typeahead'),
         re_path(r'^items/select2$', typeahead.items_select2, name='event.items.select2'),
@@ -250,6 +251,7 @@ urlpatterns = [
         re_path(r'^categories/(?P<category>\d+)/up$', item.category_move_up, name='event.items.categories.up'),
         re_path(r'^categories/(?P<category>\d+)/down$', item.category_move_down,
                 name='event.items.categories.down'),
+        re_path(r'^categories/reorder$', item.reorder_categories, name='event.items.categories.reorder'),
         re_path(r'^categories/(?P<category>\d+)/$', item.CategoryUpdate.as_view(),
                 name='event.items.categories.edit'),
         re_path(r'^categories/add$', item.CategoryCreate.as_view(), name='event.items.categories.add'),