[router][protocols] Add Axum validate extractor and use it for /v1/chat/completions endpoint (#11588)

sgl-router/tests/spec/chat_message.rs

@@ -0,0 +1,83 @@
+use serde_json::json;
+use sglang_router_rs::protocols::spec::{ChatMessage, UserMessageContent};
+
+#[test]
+fn test_chat_message_tagged_by_role_system() {
+    let json = json!({
+        "role": "system",
+        "content": "You are a helpful assistant"
+    });
+
+    let msg: ChatMessage = serde_json::from_value(json).unwrap();
+    match msg {
+        ChatMessage::System { content, .. } => {
+            assert_eq!(content, "You are a helpful assistant");
+        }
+        _ => panic!("Expected System variant"),
+    }
+}
+
+#[test]
+fn test_chat_message_tagged_by_role_user() {
+    let json = json!({
+        "role": "user",
+        "content": "Hello"
+    });
+
+    let msg: ChatMessage = serde_json::from_value(json).unwrap();
+    match msg {
+        ChatMessage::User { content, .. } => match content {
+            UserMessageContent::Text(text) => assert_eq!(text, "Hello"),
+            _ => panic!("Expected text content"),
+        },
+        _ => panic!("Expected User variant"),
+    }
+}
+
+#[test]
+fn test_chat_message_tagged_by_role_assistant() {
+    let json = json!({
+        "role": "assistant",
+        "content": "Hi there!"
+    });
+
+    let msg: ChatMessage = serde_json::from_value(json).unwrap();
+    match msg {
+        ChatMessage::Assistant { content, .. } => {
+            assert_eq!(content, Some("Hi there!".to_string()));
+        }
+        _ => panic!("Expected Assistant variant"),
+    }
+}
+
+#[test]
+fn test_chat_message_tagged_by_role_tool() {
+    let json = json!({
+        "role": "tool",
+        "content": "Tool result",
+        "tool_call_id": "call_123"
+    });
+
+    let msg: ChatMessage = serde_json::from_value(json).unwrap();
+    match msg {
+        ChatMessage::Tool {
+            content,
+            tool_call_id,
+        } => {
+            assert_eq!(content, "Tool result");
+            assert_eq!(tool_call_id, "call_123");
+        }
+        _ => panic!("Expected Tool variant"),
+    }
+}
+
+#[test]
+fn test_chat_message_wrong_role_rejected() {
+    let json = json!({
+        "role": "invalid_role",
+        "content": "test"
+    });
+
+    let result = serde_json::from_value::<ChatMessage>(json);
+    assert!(result.is_err(), "Should reject invalid role");
+}