Integrate isValidColumn in the "official" catalog API.

git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@40347 20353a03-c40f-0410-a6d1-a30d3c3de9de

product/ZSQLCatalog/interfaces/query_catalog.py

@@ -255,3 +255,10 @@ class ISearchKeyCatalog(Interface):
         identifier in SearchText is a valid column.
         If not provided, catalog schema will be used.
     """
+
+  def isValidColumn(column_id):
+    """
+      Returns wether given string is a known column.
+      Note: related keys and scriptable keys are considered columns.
+    """
+