[firestore-bigquery-export] Add lifecycle event

[joehan]

Adds lifecycle event to export existing documents to BigQuery

TODO

• Docs review from @kevinthecheung - done in firebaseprivate
• Update package-lock.json once [email protected] is published
• Code review
• Republish and test to ensure that nothing broke while switching to published deps
• Decide whether to deprecate or fully remove old import script
• Test this lifecycle hook more thoroughly - I don't have a great understanding of how the BigQuery import script should behave, so I'd like an extra look at this. Do we need to make more changes to make the import code idempotent?
• Should we add an onConfigure hook here too?

[dackers86]

@joehan

onConfigure

This event would be very useful, ideally we could use this to move the tables creation/update into the events. With this we would no longer be required to create/update the tables on each record written, which would support a few performance issues that exist in the change-tracker!

This improvement would also be added to the onInstall, onUpdate events.

Import script

It is my understanding that the import script is the only other library that uses the change-tracker dependency. Not relying on this would help with current maintenance and release constraints. I should mention this is a complex dependency. The import script also has a fair amount of users https://www.npmjs.com/package/@firebaseextensions/fs-bq-import-collection.

[dackers86]

All lifecycle hooks are included in this update.

For update and reconfiguration, the option is there to not perform the backfill. The question could be whether this enough for users to know that this will cause a new import if the value is not update?

[dackers86]

The best discussed option here is still still allow the Import script, as this is currently built into many developers workflows.

This could be still deprecated in the future