[v3] Database#on is not supporting cancel callbacks

[pedro-ribeiro]

Database#on is not supporting setting cancel callbacks. This makes it impossible to deal with Permission Denied errors.

Currently, on error the library will simply log the error message. (https://github.com/fullstackreact/react-native-firestack/blob/master/lib/modules/database.js#L401)

See Firebase documentation.

[auser]

Mmm good catch. I must have left this on the TODO. Think we should just throw a JS event back on errors?

[pedro-ribeiro]

In my opinion, it should mimic as much as possible the firebase js sdk.

[janvogt]

+1
Need this too. Relevant documentation is https://firebase.google.com/docs/reference/js/firebase.database.Reference#on