Add manual routing policy for router (#15586)

sgl-model-gateway/tests/spec/embedding.rs

@@ -10,6 +10,7 @@ fn test_embedding_request_serialization_string_input() {
         user: Some("user-1".to_string()),
         dimensions: Some(128),
         rid: Some("rid-123".to_string()),
+        routing_id: None,
         log_metrics: None,
     };
 
@@ -33,6 +34,7 @@ fn test_embedding_request_serialization_array_input() {
         user: None,
         dimensions: None,
         rid: None,
+        routing_id: None,
         log_metrics: None,
     };
 
@@ -51,6 +53,7 @@ fn test_embedding_generation_request_trait_string() {
         user: None,
         dimensions: None,
         rid: None,
+        routing_id: None,
         log_metrics: None,
     };
     assert!(!req.is_stream());
@@ -67,6 +70,7 @@ fn test_embedding_generation_request_trait_array() {
         user: None,
         dimensions: None,
         rid: None,
+        routing_id: None,
         log_metrics: None,
     };
     assert_eq!(req.extract_text_for_routing(), "hello world");
@@ -81,6 +85,7 @@ fn test_embedding_generation_request_trait_non_text() {
         user: None,
         dimensions: None,
         rid: None,
+        routing_id: None,
         log_metrics: None,
     };
     assert_eq!(req.extract_text_for_routing(), "");
@@ -95,6 +100,7 @@ fn test_embedding_generation_request_trait_mixed_array_ignores_nested() {
         user: None,
         dimensions: None,
         rid: None,
+        routing_id: None,
         log_metrics: None,
     };
     // Only top-level string elements are extracted