Which ways federated sign-in goes, each on unless set to 0.

• incoming (GERBEUR_FEDERATION_INCOMING): users of other instances sign in here. Off, the login and register pages offer no other instance, /manage lists only the blocked ones, which this instance's users can't sign in to (and none with outgoing off too), federation-service.ts refuses their sign-ins, and the accounts that came from one are signed out (getSessionState) until it is on again. Their homes' events are still applied, so that none is lost meanwhile.
• outgoing (GERBEUR_FEDERATION_OUTGOING): this instance's users sign in to others. Off, identity-provider-service.ts lets no instance sign them in, and its metadata says so, which the others check before sending anyone here to sign in. The settings page lists no instances, since at startup main.ts withdraws every grant they gave, which signs them out there.

index.html tells the client both. An object, so that the tests can turn one off for a while.