Create non-std version of TokenResponse.parse to cater for missing access_token member

[Yavor Vasilev]

Response from  

https://icmb2c.b2clogin.com/tfp/----blanked-out----/b2c_1_signupsignin1/v2.0/

Token response.

{
   "id_token":"eyJ0eXAiOiJKV1QiLCJhbGciOiJSUzI1NiIsImtpZCI6Ilg1ZVhrNHh5b2pORnVtMWtsMll0djhkbE5QNC1jNTdkTzZRR1RWQndhTmsifQ.eyJ...",
   "token_type":"Bearer",
   "not_before":1592473036,
   "id_token_expires_in":3600,
   "profile_info":"eyJ2ZXIi...",
   "scope":"openid"
}

‌

[Yavor Vasilev]

ID token header:

{"typ":"JWT","alg":"RS256","kid":"X5eXk4xyojNFum1kl2Ytv8dlNP4-c57dO6QGTVBwaNk"}

‌

[Yavor Vasilev]

Non-std behaviour.

To work around insert dummy access_token field into input before calling TokenResponse.parse.