If this hook fails, oauth2_reply/2 returns a text/plain
document with the obtained information. This can be used for
debugging and development purposes.
| Request | - is the HTTP request dealing with the redirect back from the identity provider. |
| ServerID | - identifies the identity provider. |
| TokenInfo | - is a dict containing information about the access token. |
| UserInfo | - is a dict containing information about the user. |