Migrate firebase API from legacy to v1

[timobrembeck]

Motivation

At the moment, we use the legacy fcm endpoint, but v1 was released quite a while ago and seems more future proof.

Proposed Solution

• Follow this guide to migrate the api client

Alternatives

Even though the API is called "legacy", I'm pretty sure it's still very commonly used and won't just suddenly disappear. I wouldn't be surprised if the legacy endpoint lives longer than our CMS.

Additional Context

Design Requirements

[sarahsporck]

I'd be open to do this, but I don't have the necessary permissions, to get the new 1) projectId and 2) the new authentication token.

[timobrembeck]

maybe @svenseeberg can help?

[dkehne]

@svenseeberg what is the status here?

[svenseeberg]

The Firebase project is mainly managed by the app developers. David has also access now.