Add paygate module to r402-http server feature

* Add paygate module declaration under server feature gate
* Position paygate module before server module in declaration order

Author: gitctrlx

r402-http/src/lib.rs

@@ -22,6 +22,8 @@ pub mod client;
 #[cfg(feature = "client")]
 pub mod facilitator;
 
+#[cfg(feature = "server")]
+pub mod paygate;
 #[cfg(feature = "server")]
 pub mod server;
 #[cfg(feature = "server")]