Allow to use event meta data in email templates

src/pretix/base/models/orders.py

@@ -661,6 +661,9 @@ class Order(LockModel, LoggedModel):
         if not self.email:
             return
 
+        for k, v in self.event.meta_data.items():
+            context['meta_' + k] = v
+
         with language(self.locale):
             recipient = self.email
             try: