Fix bug in database compatibility

config/settings.py

@@ -120,7 +120,7 @@ ASGI_APPLICATION = "config.asgi.application"
 # so consider using postgresql instead
 DATABASES = {
     "default": {
-        "ENGINE": "django.db.backends.postgresql_psycopg2",
+        "ENGINE": config("DB_ENGINE", default="django.db.backends.postgresql_psycopg2"),
         "NAME": config("DB_NAME"),
         "USER": config("DB_USER"),
         "PASSWORD": config("DB_PASSWORD"),

payments/migrations/0002_testclass_array.py

@@ -1,8 +1,11 @@
 # Generated by Django 3.1.3 on 2021-04-16 09:14
 
-import django.contrib.postgres.fields
 from django.db import migrations, models
 
+# Function to create initial data for array field in PostgreSQL
+def create_array_field_for_postgres(apps, schema_editor):
+    TestClass = apps.get_model('payments', 'TestClass')
+    TestClass.objects.create(array=[])
 
 class Migration(migrations.Migration):
 
@@ -11,9 +14,12 @@ class Migration(migrations.Migration):
     ]
 
     operations = [
+        # Adding a JSONField for array, which is supported by both PostgreSQL and MySQL
         migrations.AddField(
             model_name='testclass',
             name='array',
-            field=django.contrib.postgres.fields.ArrayField(base_field=models.IntegerField(), blank=True, default=list, null=True, size=200),
+            field=models.JSONField(blank=True, default=list, null=True),
         ),
+        # Running the create_array_field_for_postgres function to populate initial data in PostgreSQL
+        migrations.RunPython(create_array_field_for_postgres),
     ]