Push notifications through FCM should not have required title and body

[MHEien]

🔖 Enhancement description

FCM does not require you to pass a title and body in push notifications, and nor should Appwrite.

🎤 Pitch

Many apps benefit of data-only notifications, and it would be loevely for Appwrite to support this by removing this restriction.
In cases we would send status updates in a single notification, we could leverage this feature.

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• I checked and didn't find similar issue

🏢 Have you read the Code of Conduct?

• I have read the Code of Conduct

[stnguyen90]

@MHEien, thanks for raising this issue! 🙏🏼 Can you expand more on the use-case for data-only notifications?

[ItzNotABug]

@MHEien, thanks for raising this issue! 🙏🏼 Can you expand more on the use-case for data-only notifications?

This helps in performing any sort of update in the Apps after receiving data only messages. This doesn't bother the user to open the app as there's no notification. Assume a cache clearing task, fresh fetch task from API if its cached due to new content, etc.