Fix Spontaneous Multiplication of Push Notifications

[PeterNerlich]

Short description

Sometimes, the Firebase API seems to not provide a message_id for submitted push notifications, while it is still received on subscribed devices. As it still sent HTTP status code 200, we assumed message_id was there and tried logging it, causing an exception. This lead to resend attempts and thus multiplied push notifications.

Proposed changes

• Log API full response if no message_id is received on submitting a push notification, to gather further information
• Deliberately don't raise an exception since PNs seem to be sent correctly, (but avoid previous exception from failing to log non-existent dict field)

Side effects

• Scenarios where a push notification might fail with an error in the API response, but HTTP code 200, will not be retried. Instances of this will only be visible from the logs.

Resolved issues

Fixes: #1630

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[codeclimate]

Code Climate has analyzed commit b393ba7 and detected 1 issue on this pull request.

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Category	Count
Complexity	1

The test coverage on the diff in this pull request is 0.0% (50% is the threshold).

This pull request will bring the total coverage in the repository to 74.3%.

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[ulliholtgrave]

Looks good. I wasn't able to reproduce this issue locally, but your explanation makes sense and I would be up for bringing this on production 👍

[timobrembeck]

Looks good! 👍
Thanks a lot for investigating the problem and for the detailed explanation 🙏

[PeterNerlich]

Further detail that might be helpful: If I didn't get it wrong while quickly googling this, this section of the API doc outlines some error conditions while still sending HTTP status code 200.