Capture access token from IdP

[shawnhankim]

Background:

• Current NJS implementation disregard the access_token that is being sent by the IdP and only uses the id_token to get stored in the NGINX Plus K/V store.

• Token Recommandation

  When Using	Do	Don't
  ID Token	- Assume the user is authenticated	- Call an API
  	- Get user profile data	- Check if the client is allowed to access something.
  Access Token	- Call an API	- Inspect its content on the client
  	- Check if the client is allowed to access something
  	- Inspect its content on the server side

  courtesy: ID Token and Access Token: What's the Difference?
  

Acceptance Criteria:

• Enhance the NJS Code to capture the access_token sent by the IdP.
• Store the access_token in the k/v store as same as we store id_token and refresh_token

Compatibility:

• This issue will not block the existing features as there would be no change of variables, and this is just to add features.

[shawnhankim]

@route443 : You can use this PR if you want to test the access token.

[shawnhankim]

Per discussion with @route443 : I close this PR because I have consolidated this PR into #55. Thanks @route443 for your time. 👍