add gateway_subscriber_url to cashierd config file

src/cli/cli_config.rs

@@ -84,6 +84,9 @@ pub struct CashierdConfig {
     #[serde(rename = "gateway_url")]
     pub gateway_url: String,
 
+    #[serde(rename = "gateway_subscriber_url")]
+    pub gateway_subscriber_url: String,
+
     #[serde(rename = "log_path")]
     pub log_path: String,