required_login_params to verify required options prior to instantiating ...

...a gateway

Gateway class is inherited by all gateways. A static class method is introduced to the Gateway class: required_login_params that returns an array of default required params (most commonly found amongst all gateways). For custom required params each gateway can override the self.required_login_params method. This method should always return an array. Also in case a user is accessing each gateway in some crazy batch and ends up creating a new instance every time (very inefficient but people do stuff like this), the required_login_params array is static to help prevent inefficient calls to the method.