title: TFS REST API: How to "Make requests on behalf of others"?
body: <p>I want my VSTS extension (installed on-prem TFS2015.3) to be able to do specific requests on behalf of a admin/service account ("Make requests on behalf of others")</p>
  
  <p>Background: I manipulate (WorkItem) Process Template, specifically the GLOBALWORKFLOW (only on team-project level) in my extensions typescript, but the user of the extension in Web Access is NOT a project-admin so he is not allowed to use the function updateWorkItemTypeDefinition() - Non-Project-Admins get "Access denied" even if I gave that custom group every permission available ("Edit project-level-information" permissions for project-level GLOBALWORKFLOWs? Still didn't work for custom groups, only for Project Admin Accounts).</p>
  
  <p>It seems I'm forced to impersonate a project admin /service account which is allowed to change the global workflow in the project</p>
  
  <p>How do I impersonate in extension typescript code on-prem TFS and REST (1. not .NET and 2. without changing to basic auth, saw that solution already somewhere else - but I'm very sure I cannot request that change in my organization)</p>
  
  <p>Thanks for your help</p>