Adding customizable logoutUrl for generic oAuth2 / OpenId connect

[PheelTi]

Description

Adding a option to call a logout URL on the remote issuer for oauth/OIDC.

Closes #(issue_number)

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[Ludy87]

As far as I know, the logout URL is provided by the provider

[PheelTi]

Hello,
yes, that is true, the "generic" config do not use it though.

Depending on the provider, you might pass the client_id, and/or id_token (full token), and/or a redirect URL, and each provider may have specific attribute names for those.

This PR let you specify it for generic configuration.