[mail] include Date header in generated mails (closes #5271058)
Mails without Date gets flagged as spam. Plus it's wrong anyway.
sync_schema_props_perms('state_of')
sync_schema_props_perms('transition_of')
sync_schema_props_perms('State')
sync_schema_props_perms('BaseTransition')
sync_schema_props_perms('Transition')
sync_schema_props_perms('WorkflowTransition')