Simplified thumbnail logic, only the best thumbnail size is downloaded and then it is resized and cropped to an appropriate size for use in the web UI.

app/YtManagerApp/migrations/0011_auto_20190819_1613.py

@@ -0,0 +1,21 @@
+# Generated by Django 2.2.4 on 2019-08-19 16:13
+
+from django.db import migrations
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('YtManagerApp', '0010_auto_20190819_1317'),
+    ]
+
+    operations = [
+        migrations.RemoveField(
+            model_name='subscription',
+            name='icon_default',
+        ),
+        migrations.RemoveField(
+            model_name='video',
+            name='icon_default',
+        ),
+    ]

app/YtManagerApp/migrations/0012_auto_20190819_1615.py

@@ -0,0 +1,23 @@
+# Generated by Django 2.2.4 on 2019-08-19 16:15
+
+from django.db import migrations
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('YtManagerApp', '0011_auto_20190819_1613'),
+    ]
+
+    operations = [
+        migrations.RenameField(
+            model_name='subscription',
+            old_name='icon_best',
+            new_name='thumbnail',
+        ),
+        migrations.RenameField(
+            model_name='video',
+            old_name='icon_best',
+            new_name='thumbnail',
+        ),
+    ]