firebase/firebase-admin-node

AI Summary: The task is to modify the Firebase Admin Node.js SDK's authentication module to handle the `FIREBASE_AUTH_EMULATOR_HOST` environment variable differently. Currently, the variable is checked on every API call, affecting all initialized Firebase apps. The solution requires changing the SDK to read and store the emulator host configuration only once during app initialization, instead of repeatedly checking the environment variable. This will allow multiple Firebase apps (one using the emulator, another using the production environment) to coexist within the same process.