I have a site workflow that updates an item in a list, then I want it to publish a specific wiki page in a library on the same site.  If I was using a list workflow, I could use the Set Approval Status action, but this action is not available in site workflows.  Is there a way to publish the wiki page that doesn't require credentials?  I'm trying to avoid the Call Web Service action because the password for any credentials I supply will expire, causing the workflow to error.

I tried using the Update Item and Update Multiple Items actions, but these don't allow updating the Approval Status field for the wiki page.