//sdk/com.adobe.express.embedsdk/HostCallbackHandler/onSignInRequired
fun onSignInRequired(reason: String?, complete: (credentials: SignInCredentials?) -> Unit): Boolean
Dispatches a mid-session sign-in request to the host. Returns true if a handler was wired and invoked, false if the host never registered onSignInRequired — the caller resets its in-flight state on false so a missing callback can’t permanently wedge the action.