[credit card] implement payment

uncloud_pay/migrations/0007_auto_20201228_2338.py

@@ -0,0 +1,17 @@
+# Generated by Django 3.1 on 2020-12-28 23:38
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('uncloud_pay', '0006_auto_20201228_2337'),
+    ]
+
+    operations = [
+        migrations.AddConstraint(
+            model_name='stripecreditcard',
+            constraint=models.UniqueConstraint(condition=models.Q(active=True), fields=('owner',), name='one_active_card_per_user'),
+        ),
+    ]