title: How to get client_assertion for my certificate
body: <p>I am trying to write an application to fetch data from Office 365 (using EWS and Graph APIs). I need to write this app in C++ (for platform compatibility) and I need to use certificate based method (I don't want to use client secret based authentication). I am using Client credentials grant flow so there is no user interaction involved.</p>
  <p>I am not able to figure out how can I get client_assertion for my certificate. Is there any standard method to get this string?</p>
  <p>Thanks.</p>