Runtime External IdP configuration payload.
An External IdP client bound to the resolved configuration.
redirectUri is optional and captured once at factory creation time. When omitted,
Android delegates Custom Tab redirects to the native appRedirectUriScheme manifest
placeholder; provide it when you need Auth Tab support with a specific app return URI.
Logger integration is optional and uses logger(...).nativeHandle.id when provided.
Creates a reusable External IdP client instance for Journey flows.