feat: add replica-aware relay-to-relay forwarding

common/src/protocol.rs

@@ -45,6 +45,18 @@ pub struct StreamClosed {
     pub reason: Option<String>,
 }
 
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct RelayForwardPrelude {
+    pub version: u8,
+    pub session_id: String,
+    pub fqdn: String,
+    pub stream_id: String,
+    pub peer_addr: String,
+    pub origin_instance_id: String,
+    pub hop_count: u8,
+    pub initial_data: Vec<u8>,
+}
+
 #[derive(Debug, Clone, Serialize, Deserialize)]
 #[serde(tag = "type", content = "data")]
 pub enum ClientFrame {