getRedirectResult() always returns null - Unable to retrieve idToken after signInWithRedirect()

### Version info

**Angular:** 15

**Firebase:** 9

**AngularFire:** 7.5.0

### How to reproduce these conditions

**Steps to set up and reproduce**

> Note: I am testing this locally and on a mobile device. In both cases I am using Chrome. The application is hosted locally running `ng serve --watch --ssl --host 0.0.0.0` which means the SSL certificate is not valid. I mention this in case it is relevant.

I'm simply calling `signInWithRedirect()` and install an `APP_INITIALIZER` provider to make sure the `idToken` is loaded as the app starts.

However, the `idToken` (as well as the `credentials`) are always `null`/`undefined` and I have no idea why. Could be related to (https://github.com/angular/angularfire/issues/3208).

```typescript
public signInWithGoogle() {
return signInWithRedirect(this.auth, new GoogleAuthProvider());
}
```

```typescript
export const AUTH_ID_TOKEN_INITIALIZER_PROVIDER: Provider = {
provide: APP_INITIALIZER,
deps: [NGXLogger, AuthService],
multi: true,
useFactory: (logger: NGXLogger, authService: AuthService) => {
return async () => {
logger.info("Initializing App: Waiting for (API) idToken");
const credentials = await getRedirectResult(authService.auth);
console.log(credentials); // Is already null
const idToken = await credentials?.user.getIdToken();
console.log(idToken);
if (idToken) {
return idToken;
}
await authService.init(); // <-- Implementation below (put it here for testing)
return firstValueFrom(authService.idToken$);
}
},
};
```

I tried a different approach after reading that we have to wait for `onAuthStateChanged()` to fire and only after that we're supposed to fetch the `idToken`. The implementation looked like this (with the same result however):

```typescript
async init() {
this.logger.debug("Checking for token from redirect");
const credentials = await getRedirectResult(this.auth);
this.idToken = await credentials?.user.getIdToken();

await this.auth.onAuthStateChanged(
async () => {
const credentials = await getRedirectResult(this.auth);
this.idToken = await credentials?.user.getIdToken();
console.log("inner");
console.log(this.idToken);
}
);
console.log("outer");
console.log(this.idToken);
}
```

### Expected behavior

Receive a valid `idToken` after beind redirected.

### Actual behavior

Credentials & token are `null` / `undefined`.

首先使用 Angular 15、Firebase 9 和 AngularFire 7.5.0 重現 redirect 流程，重點關注 signInWithRedirect()、getRedirectResult()、APP_INITIALIZER 和 onAuthStateChanged()。追蹤 getRedirectResult() 的呼叫時機，並透過在 redirect 後接收到有效的 credential 和 idToken 來驗證流程已完成。

由索引模型根據 Issue 內容生成。