Revert "*: providers and sources -> channels, PolicyModel to PolicyBindingModel that uses custom M2M through"

This reverts commit 7ed3ceb960.

passbook/core/migrations/0002_nonce_description.py

@@ -0,0 +1,18 @@
+# Generated by Django 2.2.6 on 2019-10-10 11:48
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ("passbook_core", "0001_initial"),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name="nonce",
+            name="description",
+            field=models.TextField(blank=True, default=""),
+        ),
+    ]