configure static method
Sets app-level defaults for all PayWithPayStack calls.
Call this once in main() (or your DI setup) so that secretKey,
currency, and callbackUrl can be omitted on individual calls.
PayWithPayStack.configure(PaystackConfig(
secretKey: 'sk_live_xxxx',
currency: 'GHS',
callbackUrl: 'https://my-app.com/callback',
enableLogging: kDebugMode,
));
Implementation
static void configure(PaystackConfig config) {
_globalConfig = config;
}