Translate question options in backend and PDFs (Z#23134850) (#3693)

* Translate question options in backend and PDFs

* Extend to invoices

src/pretix/base/models/orders.py

@@ -1271,6 +1271,21 @@ class QuestionAnswer(models.Model):
         return self.file.name.split('.', 1)[-1]
 
     def __str__(self):
+        return self.to_string(use_cached=True)
+
+    def to_string_i18n(self):
+        return self.to_string(use_cached=False)
+
+    def to_string(self, use_cached=True):
+        """
+        Render this answer as a string.
+
+        :param use_cached: If ``True`` (default), choice and multiple choice questions will show their cached
+                           value, i.e. the value of the selected options at the time of saving and in the language
+                           the answer was saved in. If ``False``, the values will instead be loaded from the
+                           database, yielding current and translated values of the options. However, additional database
+                           queries might be required.
+        """
         if self.question.type == Question.TYPE_BOOLEAN and self.answer == "True":
             return str(_("Yes"))
         elif self.question.type == Question.TYPE_BOOLEAN and self.answer == "False":
@@ -1305,6 +1320,8 @@ class QuestionAnswer(models.Model):
                 return PhoneNumber.from_string(self.answer).as_international
             except NumberParseException:
                 return self.answer
+        elif self.question.type in (Question.TYPE_CHOICE, Question.TYPE_CHOICE_MULTIPLE) and self.answer and not use_cached:
+            return ", ".join(str(o.answer) for o in self.options.all())
         else:
             return self.answer