title: Google Action (Dialogflow) Account Linking not reliable during testing
body: <p>I'm having a lot of trouble testing my google action's account linking.  It uses the authorization oauth2 flow for account linking.  I do not have transactions enabled but instead have required sign-in on the welcome intent and both of my other (custom) intents.</p>
  
  <p>Immediately after implementing account linking, I tested the flow via the simulator and it worked perfectly.  I then wanted to link my google account to a different account on my server, which means I needed to unlink and then link again.  This is where things get fuuuuunky.</p>
  
  <p>It looks like the docs are a bit outdated, but I eventually found a way to unlink, at least partially.  The note in the blue box at the bottom of <a href="https://developers.google.com/actions/identity/account-linking" rel="nofollow noreferrer">this page</a> notes that you can unlink by disabling testing.  The UI looks different from the screenshot, but I disabled testing within the Action Simulator UI by toggling 'Testing on Device'.  I then re-enabled it and indeed my requests were no longer getting access tokens!</p>
  
  <p>However, at this point, the linking flow was no longer being invoked when I ran commands via the simulator.  I waited for a few hours and tried again - no dice.  My dialogflow webhook simply isn't getting an access_token in the request body (property no longer exists), which is good, but I'm never prompted to re-link the account.</p>
  
  <p>I tried the same using the Google Assistant app on a phone registered to my google account (same Google account being used in the simulator).  Again, it worked the first time but after I toggled testing on my device, it started to fail permanently.  So it seems device-specific? I did try an incognito chrome session as well as deleting cookies, neither of which worked.</p>
  
  <p>Any ideas how I can properly unlink and then re-link my account during testing of a google action?</p>
  
  <p>Thanks!</p>