SuggestStore

The store is the entry point to the Suggest component. It incrementally downloads suggestions from the Remote Settings service, stores them in a local database, and returns them in response to user queries.

Your application should create a single store, and manage it as a singleton. The store is thread-safe, and supports concurrent queries and ingests. We expect that your application will call `SuggestStore::query()` to show suggestions as the user types into the address bar, and periodically call `SuggestStore::ingest()` in the background to update the database with new suggestions from Remote Settings.

For responsiveness, we recommend always calling query() on a worker thread. When the user types new input into the address bar, call `SuggestStore::interrupt()` on the main thread to cancel the query for the old input, and unblock the worker thread for the new query.

The store keeps track of the state needed to support incremental ingestion, but doesn't schedule the ingestion work itself, or decide how many suggestions to ingest at once. This is for two reasons:

1. The primitives for scheduling background work vary between platforms, and aren't available to the lower-level Rust layer. You might use an idle timer on Desktop, WorkManager on Android, or BGTaskScheduler on iOS.

2. Ingestion constraints can change, depending on the platform and the needs of your application. A mobile device on a metered connection might want to request a small subset of the Suggest data and download the rest later, while a desktop on a fast link might download the entire dataset on the first launch.