Change the Endpoint for retrieving Platform Parameters

[Arjupta]

Currently the PlatformParameterService points to a demo endpoint for fetching platform parameters from the Oppia Backend. This url needs to be changed to a new endpoint after the platform parameter project gets completed. For doing so we need to first make the neccessary changes in the Oppia Backend to support the expected format of response needed and Afterwards we will raise a Pull request that changes the url in PlatformParameterService

[BenHenning]

This has actually evolved since the original issue was filed. The web team has completed a revamping of the feature flag & platform parameter system. As of now:

• Feature flags are not exposed via any endpoints for Oppia Android to consume, so we won't be able to leverage web's new feature flag functionality. We don't plan to change this until after GA.
• We're considering leveraging platform parameters for feature flags on Android, but this is still being discussed.
• Platform parameters on web currently do not support platform-specific retrieval like they did before, and this functionality is planned to be reintroduced. The platform parameter controller was also removed, so it will need to be reintroduced.

As of now, no work can be done on this until web is updated to reintroduce its platform parameter controller with support for platform evaluation (so that Android only receives Android-specific constants).

Once that's completed, the following code changes will need to be made:

• PlatformParameterService: may need updates to call into the correct handler and with the correct values.
• PlatformParameterSyncUpWorker: may need changes if the API for the service changes.
• New platform parameters should be introduced on web to introduce support for app deprecations (see notes in Implementation Request: Android Deprecation Notification #5025).

The code changes above and the end-to-end behavior will need to be verified in two stages:

• Stage 1: local verification.
  • A dev version of the web server needs to be started (with the new functionality introduced).
  • A local build of the app needs to be deployed to an emulator and configured to use the local development version of the app (see https://stackoverflow.com/a/6310592). This will require a change to NetworkConfigProdModule (to point away from oppia.org).
  • The platform parameters for app deprecation (Implementation Request: Android Deprecation Notification #5025) should be tweaked via the local dev app admin panel to deprecate the local dev app.
  • The local dev app should be verified to sync by seeing the deprecation after an app restart (need to ensure the background worker runs).
• Stage 2: production verification.
  • The app deprecation feature should be enabled in production Oppia web (without any versions being deprecated).
  • We should verify in newer versions of the app that they're logging the feature as enabled via the feature list event.

[BenHenning]

@adhiamboperes this is a critical issue for GA--I don't think we should be removing it.

[BenHenning]

oppia/oppia#21097 is the Oppia web issue that needs to be solved in tandem to this work (since it's what needs to be done in order to expose the new endpoint that will be needed by the app).