Exposes finishTransactions to flutter code

[loregr]

I've implemented a method to be able to use setFinishTransactions from Dart.

[vegaro]

Thanks for opening this @loregr

I have one question though. Are you trying to set the SDK in observer mode? Why do you need to set finishTransactions?

There's already a parameter in the setup call https://github.com/RevenueCat/purchases-flutter/blob/master/lib/purchases_flutter.dart#L34 that will let you set the SDK in observer mode in case you already have other iap system in place and you don't want our SDK to finish/consume any transaction. SetFinishTransactions is kinda the legacy way of setting the SDK in observer mode.

[loregr]

@vegaro thanks for your feedback. In my understanding (and I may be wrong) observer mode is to be used when I want only to get access to the advanced charting, webhooks, and attribution while I manage purchases and restores in a native way (or without going through revenueCat SDK).
In may case, I still handle the whole in-app purchase process using RevenueCat SDK, the only thing that I needed (and it was missing) was the possibility to don't consume the purchase because I want the user to be able to restore the purchase (no-subscription) if he uninstalls and reinstalls the app, or simply changes his device. So setting finishTransactions to false was exactly what I needed. Also, it looks like that if I want to use observer mode I must pass an appUserId, otherwise the value will be ignored, by setting finishTransactions to false instead, I don't need any additional info.

[vegaro]

I see, that makes sense. Can't you get that functionality by using the information inside PurchaserInfo? Even if that transaction has been consumed it should appear after a restore in the allPurchasedProductIdentifiers or in the entitlements if you're using the entitlements system.

(sorry it took so long to reply 🤦)

[aboedo]

@loregr
thanks so much for opening and for the feedback!
There are a couple of minor indentation issues that we should fix before merging, but we can take care of them if you don't have the time, just let us know.
Otherwise, this looks good to go.