Delete posts after a ban is created for them

After a user is banned for a post, that post now gets deleted. There's
no way to turn this off yet.

Signed-off-by: Alek Ratzloff <alekratz@gmail.com>

board/models.py

@@ -308,6 +308,14 @@ class Ban(BanCommon):
         return f"Ban for {self.ip}"
 
 
+@receiver(signals.post_save, sender=Ban)
+def ban_created(sender, instance, created, **kwargs):
+    if created:
+        if instance.post_id:
+            post = Post.objects.get(id=instance.post_id)
+            post.delete()
+
+
 class BanTemplate(models.Model):
     # The name of this template
     name = models.CharField(max_length=100)