Issue #3321915 by anybody: [8.x] Allow to store live and sandbox credentials for easy switching

config/schema/commerce_paypal.schema.yml

@@ -10,6 +10,12 @@ commerce_payment.commerce_payment_gateway.plugin.paypal_checkout:
     secret:
       type: string
       label: 'Secret'
+    sandbox_client_id:
+      type: string
+      label: 'Sandbox Client ID'
+    sandbox_secret:
+      type: string
+      label: 'Sandbox Secret'
     intent:
       type: string
       label: 'Intent'