Allow .env override in payment config

lib/common.js

@@ -249,6 +249,13 @@ const getPaymentConfig = () => {
         config = Object.assign(config, localConfigObj);
     }
 
+    // Override from .env file
+    Object.keys(config).forEach((configKey) => {
+        if(process.env[configKey]){
+            config[configKey] = process.env[configKey];
+        }
+    });
+
     return config;
 };