docs: def v1_random_fc_get(response, dbid_to_visid, store):
      '''Retrieves a random feature collection from the database.
  
      The route for this endpoint is:
      ``GET /dossier/v1/random/feature-collection``.
  
      Assuming the database has at least one feature collection,
      this end point returns an array of two elements. The first
      element is the content id and the second element is a
      feature collection (in the same format returned by
      :func:`dossier.web.routes.v1_fc_get`).
  
      If the database is empty, then a 404 error is returned.
  
      Note that currently, this may not be a uniformly random sample.
      '''
      # Careful, `store.scan()` would be obscenely slow here...
      sample = streaming_sample(store.scan_ids(), 1, 1000)
      if len(sample) == 0:
          bottle.abort(404, 'The feature collection store is empty.')
      return [dbid_to_visid(sample[0]), util.fc_to_json(store.get(sample[0]))]