title: Client Credential Gran Type Not Support with a Custom B2C Policy
body: <p>I am trying to generate an access token from our policy but I am getting this error.</p>
  
  <pre><code>AADB2C90086: The supplied grant_type [client_credentials] is not supported.
  </code></pre>
  
  <p>This is a sample postman request</p>
  
  <pre><code>POST /{tenant}/oauth2/token?p=B2C_1A_SignUpOrSignInWithAAD HTTP/1.1
  Host: login.microsoftonline.com
  Content-Type: application/x-www-form-urlencoded
  Cache-Control: no-cache
  
  grant_type=client_credentials&amp;client_id={client_id}&amp;resource=https%3A%2F%2F{app_url}&amp;client_secret={client_secret}
  </code></pre>
  
  <p>but it works fine if I don't use our custom policy and just go direct to the B2C tenant</p>
  
  <pre><code>POST /{tenant}/oauth2/token?api-version=1.0
  ... same as above
  </code></pre>
  
  <p>Is there something missing in our custom policy?</p>