[router] allow user to specify chat template path (#11549)

sgl-router/tests/api_endpoints_test.rs

@@ -30,6 +30,7 @@ impl TestContext {
     async fn new(worker_configs: Vec<MockWorkerConfig>) -> Self {
         // Create default router config
         let config = RouterConfig {
+            chat_template: None,
             mode: RoutingMode::Regular {
                 worker_urls: vec![],
             },
@@ -1365,6 +1366,7 @@ mod error_tests {
     async fn test_payload_too_large() {
         // Create context with small payload limit
         let config = RouterConfig {
+            chat_template: None,
             mode: RoutingMode::Regular {
                 worker_urls: vec![],
             },
@@ -1723,6 +1725,7 @@ mod pd_mode_tests {
             .unwrap_or(9000);
 
         let config = RouterConfig {
+            chat_template: None,
             mode: RoutingMode::PrefillDecode {
                 prefill_urls: vec![(prefill_url, Some(prefill_port))],
                 decode_urls: vec![decode_url],
@@ -1888,6 +1891,7 @@ mod request_id_tests {
     async fn test_request_id_with_custom_headers() {
         // Create config with custom request ID headers
         let config = RouterConfig {
+            chat_template: None,
             mode: RoutingMode::Regular {
                 worker_urls: vec![],
             },