Merged in hotfix/defensive-crosswalk (pull request #632)

Hotfix/defensive crosswalk handling

* Enhance crosswalk functionality with flatten_to_strings helper and improve value handling in apply_crosswalk

* Improve apply_crosswalk function to return original value as fallback when no mapping is found

* Enhance apply_crosswalk function to handle empty values and improve defensive programming tests

* move flatten_to_strings helper function to string_utils


Approved-by: Katon Minhas

fieldExtraction/src/utils/string_utils.py

@@ -587,3 +587,24 @@ def normalize_state_to_abbreviation(state_value: str) -> str:
 
     # If no match found, return original value
     return state_value
+
+def flatten_to_strings(items) -> list[str]:
+    """Helper function to flatten and stringify any nested structure
+
+    Args:
+        items (Any): The input items; can be a list, tuple, or single value
+
+    Returns:
+        list[str]: A flattened list of stringified items
+    """
+    result = []
+    if isinstance(items, (list, tuple)):
+        for item in items:
+            if isinstance(item, (list, tuple)):
+                result.extend(flatten_to_strings(item))
+            else:
+                result.append(str(item).strip())
+    else:
+        result.append(str(items).strip())
+    
+    return result