Interface FederationProviderHandle

Minimal structural type for a federation provider as seen from ContributesMap.federations consumers via the federationProviders synthetic key.

FederationProvider from @o3co/auth-provider-session carries the full capability surface (buildAuthorizationUrl, exchangeCode, optional endSession / mapClaims / refreshToken). Core cannot import that type directly — it would create a circular dependency. This structural alias captures only the shape that oauth/routes and similar core-adjacent consumers use when looking up providers from the synthetic-key map. They narrow with instanceof / type-guard helpers (supportsLogout, supportsRefresh) after reading from the map.