FR: Adding Proxy Fields to AndroidNotification Struct

[byungwoo-Nam]

Hello.

In the Cloud Messaging feature, you need to add a Proxy variable to the AndroidNotification type.

Related documents are as follows
FCM REST API document
Proxy setting related

When receiving FCM in a Flutter-based app, a problem occurred where the listener did not work, and it was determined to be due to the 'Notification Delegation to Google Play Services' function.
Related issue

The above problem can be solved by setting the proxy setting to DENY when sending FCM (confirm by sending directly to HTTP v1 API). However, since firebase-admin-go currently does not support separate proxy settings, I would like to add this part.

I think it is absolutely necessary to make it behave the same as HTTP v1 API regardless of the receiving environment.

I will upload PR.
Please review it!
Thank you.

[byungwoo-Nam]

It's been about a month since the PR related to the issue was merged into the dev branch, so when will the official release be?
Or is it being delayed for another reason?
If there is anything else I need to do, please feel free to let me know!
Please check and reply.
Thank you!

@lahirumaramba