Update cast_date_to_iso8601 to handle date and string (#1488)

* update cast_date_to_iso8601 to handle date and string

* add comments per gemini-code-assist feedback

src/ol_dbt/macros/cast_date_to_iso8601.sql

@@ -1,3 +1,8 @@
 {% macro cast_date_to_iso8601(column_name) %}
-    to_iso8601(from_iso8601_date({{ column_name }}))
+  case
+    when try_cast({{ column_name }} AS date) is not null -- Use try_cast to check if the column is already a date
+       then to_iso8601(try_cast({{ column_name }} AS date))
+
+    else to_iso8601(from_iso8601_date(try_cast({{ column_name }} AS varchar))) -- Convert to ISO 8601 from a string
+end
 {% endmacro %}