Add 'unlimited_queue_length' permission

The 'unlimited_queue_length' permission allows a user to queue
songs without being restricted by the 45-minute queue length.

marietje/queues/migrations/0009_unlimited_queue_length_perm.py

@@ -0,0 +1,17 @@
+# Generated by Django 2.2.13 on 2020-06-09 15:24
+
+from django.db import migrations
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('queues', '0008_remove_queuecommand_executed'),
+    ]
+
+    operations = [
+        migrations.AlterModelOptions(
+            name='queue',
+            options={'permissions': (('can_skip', 'Can skip the currently playing song'), ('can_move', 'Can move all songs in the queue'), ('can_cancel', 'Can cancel all songs in the queue'), ('can_control_volume', 'Can control the volume of Marietje'), ('unlimited_queue_length', 'Is unlimited by maximum queue length'))},
+        ),
+    ]