Add support for the id_token flow in the authenticator

Currently, the authenticator relies on the code flow. Some provider have a weird support of default the code flow (non-standard access to the UserInfo) and for those it would be interesting to be able to use the id_token flow (in which the user information is sent in the id token). This is for example the case of the Microsoft Identity Platform.

See https://darutk.medium.com/diagrams-of-all-the-openid-connect-flows-6968e3990660#e3eb for example for more details about the id_token flow (and others flows).