- Added PricingPlan Model

- Implement a complete cycle for buying a Matrix Chat Host
- Refactor the Payement cycle and stripe related methods

uncloud_pay/migrations/0019_order_pricing_plan.py

@@ -0,0 +1,19 @@
+# Generated by Django 3.2.4 on 2021-07-06 19:18
+
+from django.db import migrations, models
+import django.db.models.deletion
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('uncloud_pay', '0018_payment'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='order',
+            name='pricing_plan',
+            field=models.ForeignKey(null=True, on_delete=django.db.models.deletion.CASCADE, to='uncloud_pay.pricingplan'),
+        ),
+    ]