Add needs_mic property to events

RIGS/models.py

@@ -378,6 +378,10 @@ class Event(models.Model, RevisionMixin):
                 return f"N{self.pk:05d}"
             return self.pk
         return "????"
+    
+    @property
+    def needs_mic(self):
+        return self.is_rig and not self.dry_hire
 
     # Calculated values
     """