[Up for Adoption] [WIP] Fastlane automatic releases

[teolemon]

This PR aims at automating the internal release of Smoothie to the PlayStore and the App Store. It is building on work by Philippe

• At the moment, it's a copy paste of both our pipelines for iOS and Android. It's not adapted to Flutter, but we did the work of putting the secrets in safe places.
• The flutter team explains how to do it for Flutter at https://flutter.dev/docs/deployment/cd

TODO (incomplete list)

• Finish morphing the 2 series of pipelines to a single pipeline
• Change the Android key (there's a specific key for smoothie)
• Generate the appropriate iOS files

[M123-dev]

@teolemon I wanted to deal with this in the next few days, could you explain to me where you put and how encrypted the secrets, such as the Android keystore and the service account key.

I saw api-[...].json.gpg and .enc are there any differences between them or can I just use the gpg one?

[teolemon]

I did some copy pasting from Android and iOS without fully knowing what I was doing.

• Checking that the package name is the right one
• Committing the key for smoothie to the repo, just like we did for Android: https://github.com/openfoodfacts/openfoodfacts-androidapp/tree/develop/fastlane/envfiles
• Adding all the variables we need as secrets to decypher the keystore

@philippeauriach did the automation for Android, so he might have some more insight

[M123-dev]

Taken over by #96