SITE_SWITCH_SID SITE Endpoint
  /rpc/site/?method= SITE_SWITCH_SID  
  Switch to another SID. The main use of this would be when transferring between HTTP and HTTPS. Use SITE_SID_SEARCH to get the sid, switch to https, and then call this method.  
  For security, you need to be switching into a session created from the same IP address.  
  RETURN  
  TargetSID Mandatory.
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