Fix for proxy based on v5

[lucarosty]

@alex-friedl : the requested patch

[alex-friedl]

@lucarosty Thx for the PR.

Looking this through it seems you need a way to enable enableLegacyHttpTransport even though it's deprecated?

I would prefer to keep this independent of the actual proxy support as your solution could break things for users of the httpAgent setting.

Could you test #235 and let me know if it works for you?

[lucarosty]

Yes I think that this could work for enabling the legacy transport (http1/1) that is the only one that support proxy in firebase-admin.
Do not forget to add this line in the credentials:

opts.credential.httpAgent = settings.fcm.httpAgent || undefined;

[alex-friedl]

Thanks for the confirmation @lucarosty!

I think it already implements exactly what you described?

Usage Example

To use the new legacyHttpTransport feature with proxy support:

const PushNotifications = require('node-pushnotifications');

const settings = {
  fcm: {
    serviceAccountKey: require('./firebase-service-account.json'),
    // Enable HTTP/1.1 transport (required for proxy support)
    legacyHttpTransport: true,
    // Optional: Configure HTTP proxy agent
    httpAgent: new HttpProxyAgent('http://proxy.example.com:8080'),
    httpsAgent: new HttpsProxyAgent('https://proxy.example.com:8080'),
  }
};

const push = new PushNotifications(settings);

// Send notifications with proxy support
await push.send(registrationIds, {
  title: 'Hello',
  body: 'World',
});

The httpAgent setting has already been added in #230