FCM HTTP V1 API

### Step 1: Describe your environment

* Operating system: MAC OS
* Browser: CHROME
* Firebase SDK version: 9.23.0

### Step 2: Describe the problem: (1) How to send web push to multiple tokens at once in PHP using latest fcm http v1 api.
(2) compat js libs will also depreciated soon?

#### Steps to reproduce:

1. _____
2. _____
3. _____

#### Observed Results:

* What happened? This could be a description, logs, etc.

#### Expected Results:

* What did you expect to happen?

#### Relevant Code:

```
// TODO(you): code here to reproduce the problem
```