billing: Add option to request a sponsorship in /upgrade.

corporate/migrations/0009_customer_sponsorship_pending.py

@@ -0,0 +1,18 @@
+# Generated by Django 2.2.13 on 2020-06-09 12:09
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('corporate', '0008_nullable_next_invoice_date'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='customer',
+            name='sponsorship_pending',
+            field=models.BooleanField(default=False),
+        ),
+    ]