Report server version in doctor

src/bin/dosh-client.rs

@@ -606,6 +606,14 @@ async fn run_doctor_command(config: &dosh::config::ClientConfig, args: &Args) ->
     {
         Ok(check) => {
             println!("[ok] native udp: reachable");
+            println!(
+                "[ok] server version: {}",
+                if check.server_version.is_empty() {
+                    "<unknown>"
+                } else {
+                    &check.server_version
+                }
+            );
             println!("[ok] known host: trusted");
             println!("[ok] native auth: authorized as {}", check.requested_user);
             println!(

src/bin/dosh-server.rs

@@ -524,6 +524,7 @@ async fn handle_native_user_auth(
                 allow_remote_forwarding: locked.config.allow_remote_forwarding,
                 allow_agent_forwarding: locked.config.allow_agent_forwarding,
                 policy_flags: Vec::new(),
+                server_version: env!("CARGO_PKG_VERSION").to_string(),
             }
         };
         let body = protocol::to_body(&check)?;

src/protocol.rs

@@ -290,6 +290,8 @@ pub struct NativeAuthCheckOkBody {
     pub allow_remote_forwarding: bool,
     pub allow_agent_forwarding: bool,
     pub policy_flags: Vec<String>,
+    #[serde(default)]
+    pub server_version: String,
 }
 
 #[derive(Debug, Clone, Serialize, Deserialize)]