feat: add {assignee} placeholder

pretalx_musicrate/signals.py

@@ -1,9 +1,26 @@
 from django.dispatch import receiver
 from django.urls import reverse
 from django.utils.translation import gettext_lazy as _
+from pretalx.mail.placeholders import SimpleFunctionalMailTextPlaceholder
+from pretalx.mail.signals import register_mail_placeholders
 from pretalx.orga.signals import nav_event, nav_event_settings
 
 
+@receiver(register_mail_placeholders)
+def pretalx_musicrate_placeholders(sender, **kwargs):
+    return [
+        SimpleFunctionalMailTextPlaceholder(
+            "assignee",
+            ["submission"],
+            lambda submission: assignee.user.name
+            if (assignee := submission.assignee) is not None
+            else "Günther",
+            "Günther",
+            _("The name of the submission's assignee"),
+        )
+    ]
+
+
 @receiver(nav_event)
 def pretalx_musicrate_qrcode(sender, request, **kwargs):
     if not request.user.has_perm("orga.view_submissions", request.event):