title: Google Marketplace v2 install flow no notification to application that something was installed
body: <p>I'm trying to migrate our application from v1 to v2 install flow and crawling through all possible docs wasn't able to find a clear explanation of how install process work. </p>
  
  <p>I setup an application and put a link to 'Universal Navigation extension'. Google Marketplace SDK and Google Marketplace API enabled. Then when I install an app it installs on google side, but there is no callback for my application to understand that application was installed. Then when I click 'Launch App' I redirected to the link I provided, but there are no authorization or signature to verify that this request is actually from google and no clue to understand from which user it came. I assume that I can put some parameter to this URL and then use License API to get info about user, but there are no documentation about this and in old documentation looks like the only parameter available is ${DOMAIN_NAME}. </p>
  
  <p>Can somebody point me to the documentation which describe this process in more details?
  Are there any call to notify application that someone has installed their application? </p>
  
  <p>Thanks in advance!</p>