feat(trace): support external trace id propagation (#22623)

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

api/core/helper/trace_id_helper.py

@@ -0,0 +1,42 @@
+import re
+from collections.abc import Mapping
+from typing import Any, Optional
+
+
+def is_valid_trace_id(trace_id: str) -> bool:
+    """
+    Check if the trace_id is valid.
+
+    Requirements: 1-128 characters, only letters, numbers, '-', and '_'.
+    """
+    return bool(re.match(r"^[a-zA-Z0-9\-_]{1,128}$", trace_id))
+
+
+def get_external_trace_id(request: Any) -> Optional[str]:
+    """
+    Retrieve the trace_id from the request.
+
+    Priority: header ('X-Trace-Id'), then parameters, then JSON body. Returns None if not provided or invalid.
+    """
+    trace_id = request.headers.get("X-Trace-Id")
+    if not trace_id:
+        trace_id = request.args.get("trace_id")
+    if not trace_id and getattr(request, "is_json", False):
+        json_data = getattr(request, "json", None)
+        if json_data:
+            trace_id = json_data.get("trace_id")
+    if isinstance(trace_id, str) and is_valid_trace_id(trace_id):
+        return trace_id
+    return None
+
+
+def extract_external_trace_id_from_args(args: Mapping[str, Any]) -> dict:
+    """
+    Extract 'external_trace_id' from args.
+
+    Returns a dict suitable for use in extras. Returns an empty dict if not found.
+    """
+    trace_id = args.get("external_trace_id")
+    if trace_id:
+        return {"external_trace_id": trace_id}
+    return {}