Function bucket_region_get 

pub async fn bucket_region_get(
    profile_id: ProfileId,
    bucket: BucketId,
    store: State<'_, ProfileStoreHandle>,
    pool: State<'_, S3ClientPoolHandle>,
    cache: State<'_, CacheHandle>,
) -> Result<String, AppError>

Return the cached region for bucket, resolving it lazily on cache miss.

If the region is not yet known (background discovery has not finished), this command resolves it synchronously and caches the result.