Improve error messages: split validation and include field name

- Split user ID validation into two distinct error cases:
  1. Missing user ID (no valid targeting_key, user_id, or userId found)
  2. Invalid type (user ID found but not a string)
- Include original field name in type validation error for better debugging
- Re-introduce user_id_source variable for error reporting purposes only
- Enhanced error specificity: 'targeting_key must be a string, got int' vs generic message

Author: jonathannorris

devcycle_python_sdk/models/user.py

@@ -107,19 +107,28 @@ def create_user_from_context(
         :return: A DevCycleUser instance
         """
         user_id = None
+        user_id_source = None
 
         if context:
             if context.targeting_key:
                 user_id = context.targeting_key
+                user_id_source = "targeting_key"
             elif context.attributes and "user_id" in context.attributes.keys():
                 user_id = context.attributes["user_id"]
+                user_id_source = "user_id"
             elif context.attributes and "userId" in context.attributes.keys():
                 user_id = context.attributes["userId"]
+                user_id_source = "userId"
 
-        if not user_id or not isinstance(user_id, str):
+        if not user_id:
             raise TargetingKeyMissingError(
                 "DevCycle: Evaluation context does not contain a valid targeting key, user_id, or userId attribute"
             )
+        
+        if not isinstance(user_id, str):
+            raise TargetingKeyMissingError(
+                f"DevCycle: {user_id_source} must be a string, got {type(user_id).__name__}"
+            )
 
         user = DevCycleUser(user_id=user_id)
         custom_data: Dict[str, Any] = {}