OIDC: Authentik backchannel logout not working due to lack of exp in post

[PrivatePuffin]

Authentik does not contain exp in the backchannel logout post, as this is technically not required by the standard.

Yet backchannel logout on MAS fails due to this missing argument.

For more info, see:
goauthentik/authentik#16490

[sandhose]

…as this is technically not required by the standard.

I don't agree with this: https://openid.net/specs/openid-connect-backchannel-1_0.html#LogoutToken

exp REQUIRED. Expiration time, as specified in Section 2 of [OpenID.Core].

[PrivatePuffin]

https://openid.net/specs/openid-connect-backchannel-1_0.html#LogoutToken

Good call.