administration: document non obvious code in Base_checkAlarmConsistency

bt5/erp5_administration/SkinTemplateItem/portal_skins/erp5_administration/Base_checkAlarmConsistency.py

@@ -9,8 +9,11 @@ if context.providesIConstraint():
   # of this name implement consistency checking on object
   return constraint_message_list
 
+# this constraint is created as a temp object under portal_trash, because
+# portal_trash has no restriction on allowed content types.
 missing_category_document = portal.portal_trash.newContent(
   portal_type='Missing Category Document Constraint',
+  id='missing_category_document_constraint',
   temp_object=True)
 property_type_validity = PropertyTypeValidity(id='type_check', description='Type Validity Check')