increase the length of payment and subscription ext ids

payments/migrations/0007_auto_20201114_1730.py

@@ -0,0 +1,26 @@
+# Generated by Django 3.1.2 on 2020-11-14 17:30
+
+from django.conf import settings
+from django.db import migrations, models
+import django.db.models.deletion
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        migrations.swappable_dependency(settings.AUTH_USER_MODEL),
+        ('payments', '0006_auto_20190907_2029'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='payment',
+            name='backend_extid',
+            field=models.CharField(blank=True, max_length=256, null=True),
+        ),
+        migrations.AlterField(
+            model_name='subscription',
+            name='backend_extid',
+            field=models.CharField(blank=True, max_length=256, null=True),
+        ),
+    ]

payments/models.py

@@ -131,7 +131,7 @@ class Payment(models.Model, BackendData):
     subscription = models.ForeignKey('Subscription', null=True, blank=True, on_delete=models.CASCADE)
     status_message = models.TextField(blank=True, null=True)
 
-    backend_extid = models.CharField(max_length=64, null=True, blank=True)
+    backend_extid = models.CharField(max_length=256, null=True, blank=True)
     backend_data = JSONField(blank=True)
 
     @property
@@ -196,7 +196,7 @@ class Subscription(models.Model, BackendData):
     last_confirmed_payment = models.DateTimeField(blank=True, null=True)
     status = models.CharField(max_length=16, choices=SUBSCR_STATUS_CHOICES, default='new')
 
-    backend_extid = models.CharField(max_length=64, null=True, blank=True)
+    backend_extid = models.CharField(max_length=256, null=True, blank=True)
     backend_data = JSONField(blank=True)
 
     @property