Dockerfile: Use Python 3.13

Dockerfile

@@ -1,4 +1,4 @@
-FROM python:3.11-bookworm
+FROM python:3.13-trixie
 
 RUN apt-get update && \
     apt-get install -y --no-install-recommends \

src/pretix/presale/forms/checkout.py

@@ -32,8 +32,11 @@
 # distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 # License for the specific language governing permissions and limitations under the License.
 
+from itertools import chain
+
 from django import forms
 from django.core.exceptions import ValidationError
+from django.utils.encoding import force_str
 from django.utils.formats import date_format
 from django.utils.html import escape
 from django.utils.safestring import mark_safe
@@ -165,6 +168,46 @@ class QuestionsForm(BaseQuestionsForm):
             )
 
 
+class AddOnRadioSelect(forms.RadioSelect):
+    option_template_name = 'pretixpresale/forms/addon_choice_option.html'
+
+    def optgroups(self, name, value, attrs=None):
+        attrs = attrs or {}
+        groups = []
+        has_selected = False
+        for index, (option_value, option_label, option_desc) in enumerate(chain(self.choices)):
+            if option_value is None:
+                option_value = ''
+            if isinstance(option_label, (list, tuple)):
+                raise TypeError('Choice groups are not supported here')
+            group_name = None
+            subgroup = []
+            groups.append((group_name, subgroup, index))
+
+            selected = (
+                force_str(option_value) in value and
+                (has_selected is False or self.allow_multiple_selected)
+            )
+            if selected is True and has_selected is False:
+                has_selected = True
+            attrs['description'] = option_desc
+            subgroup.append(self.create_option(
+                name, option_value, option_label, selected, index,
+                subindex=None, attrs=attrs,
+            ))
+
+        return groups
+
+
+class AddOnVariationField(forms.ChoiceField):
+    def valid_value(self, value):
+        text_value = force_str(value)
+        for k, v, d in self.choices:
+            if value == k or text_value == force_str(k):
+                return True
+        return False
+
+
 class MembershipForm(forms.Form):
     required_css_class = 'required'