Resolve "review django admin panel configuration"

Closes #346 (closed)

Do you think there is something else to be done here?

smash/web/models/appointment.py

@@ -77,6 +77,14 @@ class Appointment(models.Model):
         default=False
     )
 
+    def __str__(self):
+        start = self.datetime_when.strftime('%Y-%m-%d %H:%M')
+        if self.visit is not None:
+            subject = self.visit.subject.subject
+            return f'#{self.visit.visit_number:02} | {start} ({self.length} min) | {subject.first_name} {subject.last_name} | {self.status}'
+        else:
+            return f'{start} ({self.length} min) | {self.status}'
+
     def mark_as_finished(self):
         self.status = Appointment.APPOINTMENT_STATUS_FINISHED
         self.save()