Use X-SMG-Routing-Key header instead of json body and add tests (#15826)

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

@@ -10,7 +10,6 @@ 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,
     };
 
@@ -34,7 +33,6 @@ fn test_embedding_request_serialization_array_input() {
         user: None,
         dimensions: None,
         rid: None,
-        routing_id: None,
         log_metrics: None,
     };
 
@@ -53,7 +51,6 @@ fn test_embedding_generation_request_trait_string() {
         user: None,
         dimensions: None,
         rid: None,
-        routing_id: None,
         log_metrics: None,
     };
     assert!(!req.is_stream());
@@ -70,7 +67,6 @@ 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");
@@ -85,7 +81,6 @@ 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(), "");
@@ -100,7 +95,6 @@ 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