[FR] Add subtitle for iOS push notifications

[daxaxelrod]

Describe your environment
Messaging/Notifications
Describe the problem
We cannot send push notifications with subtitle for iOS due to ApsAlert struct lacking a subtitle field.

FCM API and the APNS itself do support this field on iOS 9+ (and it's safely ignored on older versions).

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[lahirumaramba]

Hi @daxaxelrod this is the Firebase Admin Node.js repo. Do you need this feature supported in the Go SDK?

Hey, @chong-shao WDYT?

[daxaxelrod]

Hey @lahirumaramba Yes looking to get this added for the node sdk

[lahirumaramba]

I misread your comment, apologies. It looks like the subtitle field is available in the Node.js SDK. See https://firebase.google.com/docs/reference/admin/node/firebase-admin.messaging.apsalert.md#apsalertsubtitle

Does that help?

[daxaxelrod]

No problem! I've tried that (at least on v11.9.0) and it wasn't working for me. Am only able to get the title and body to work