Replace SCSS compilation with CSS variables (#4191)

* Replace SCSS compilation with CSS variables

* Update tests

* Update src/pretix/presale/style.py

Co-authored-by: Mira <weller@rami.io>

* Update src/pretix/presale/context.py

Co-authored-by: Mira <weller@rami.io>

* Update src/pretix/presale/views/widget.py

Co-authored-by: Mira <weller@rami.io>

* Update src/pretix/presale/context.py

Co-authored-by: Mira <weller@rami.io>

* Update src/pretix/static/pretixbase/scss/_variables.scss

Co-authored-by: Richard Schreiber <schreiber@rami.io>

* Last minor changes

* Rename file

---------

Co-authored-by: Mira <weller@rami.io>
Co-authored-by: Richard Schreiber <schreiber@rami.io>

src/pretix/base/models/event.py

@@ -789,8 +789,6 @@ class Event(EventMixin, LoggedModel):
         ), tz)
 
     def copy_data_from(self, other, skip_meta_data=False):
-        from pretix.presale.style import regenerate_css
-
         from ..signals import event_copy_data
         from . import (
             Discount, Item, ItemAddOn, ItemBundle, ItemCategory, ItemMetaValue,
@@ -1011,10 +1009,10 @@ class Event(EventMixin, LoggedModel):
                 s.product = item_map[s.product_id]
             s.save(force_insert=True)
 
-        has_custom_style = other.settings.presale_css_file or other.settings.presale_widget_css_file
         skip_settings = (
             'ticket_secrets_pretix_sig1_pubkey',
             'ticket_secrets_pretix_sig1_privkey',
+            # no longer used, but we still don't need to copy them
             'presale_css_file',
             'presale_css_checksum',
             'presale_widget_css_file',
@@ -1057,9 +1055,6 @@ class Event(EventMixin, LoggedModel):
             question_map=question_map, checkin_list_map=checkin_list_map, quota_map=quota_map,
         )
 
-        if has_custom_style:
-            regenerate_css.apply_async(args=(self.pk,))
-
     def get_payment_providers(self, cached=False) -> dict:
         """
         Returns a dictionary of initialized payment providers mapped by their identifiers.
@@ -1337,18 +1332,12 @@ class Event(EventMixin, LoggedModel):
 
     def enable_plugin(self, module, allow_restricted=frozenset()):
         plugins_active = self.get_plugins()
-        from pretix.presale.style import regenerate_css
-
         if module not in plugins_active:
             plugins_active.append(module)
             self.set_active_plugins(plugins_active, allow_restricted=allow_restricted)
 
-        regenerate_css.apply_async(args=(self.pk,))
-
     def disable_plugin(self, module):
         plugins_active = self.get_plugins()
-        from pretix.presale.style import regenerate_css
-
         if module in plugins_active:
             plugins_active.remove(module)
             self.set_active_plugins(plugins_active)
@@ -1357,8 +1346,6 @@ class Event(EventMixin, LoggedModel):
             if module in plugins_available and hasattr(plugins_available[module].app, 'uninstalled'):
                 getattr(plugins_available[module].app, 'uninstalled')(self)
 
-        regenerate_css.apply_async(args=(self.pk,))
-
     @staticmethod
     def clean_has_subevents(event, has_subevents):
         if event is not None and event.has_subevents is not None:

src/pretix/base/settings.py

@@ -2851,22 +2851,6 @@ Your {organizer} team"""))  # noqa: W291
             **primary_font_kwargs()
         ),
     },
-    'presale_css_file': {
-        'default': None,
-        'type': str
-    },
-    'presale_css_checksum': {
-        'default': None,
-        'type': str
-    },
-    'presale_widget_css_file': {
-        'default': None,
-        'type': str
-    },
-    'presale_widget_css_checksum': {
-        'default': None,
-        'type': str
-    },
     'logo_image': {
         'default': None,
         'type': File,
@@ -3396,10 +3380,6 @@ Your {organizer} team"""))  # noqa: W291
         'type': str,
     }
 }
-SETTINGS_AFFECTING_CSS = {
-    'primary_color', 'theme_color_success', 'theme_color_danger', 'primary_font',
-    'theme_color_background', 'theme_round_borders'
-}
 PERSON_NAME_TITLE_GROUPS = OrderedDict([
     ('english_common', (_('Most common English titles'), (
         'Mr',