add docs to GCHandshake

common/src/lib.rs

@@ -104,12 +104,17 @@ pub trait JobMultiple {
     fn completed(&self) -> bool;
 }
 
+/// Trait for game-specific game-coordinator handshakes
 pub trait GCHandshake {
+    /// The type of message send to the game-coordinator during handshake
     type Hello: RpcMessageWithKind + Send;
 
+    /// The expected response type from the game-coordinator to our hello
     type Welcome: RpcMessageWithKind + Send;
 
+    /// The steam app id we're getting the game-coordinator for
     fn app_id(&self) -> u32;
 
+    /// An instance of the hello message to send
     fn hello(&self) -> Self::Hello;
 }