[credit card] implement payment

uncloud_pay/migrations/0002_auto_20201228_2244.py

@@ -0,0 +1,24 @@
+# Generated by Django 3.1 on 2020-12-28 22:44
+
+import django.core.validators
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('uncloud_pay', '0001_initial'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='payment',
+            name='currency',
+            field=models.CharField(choices=[('CHF', 'Swiss Franc'), ('EUR', 'Euro'), ('USD', 'US Dollar')], default='CHF', max_length=32),
+        ),
+        migrations.AlterField(
+            model_name='payment',
+            name='amount',
+            field=models.DecimalField(decimal_places=2, max_digits=10, validators=[django.core.validators.MinValueValidator(0)]),
+        ),
+    ]