Since completion suggester for ElasticSearch experiments have positive indications, we may want to create a permanent mainstream documented API that provides suggestions for completion boxes. This API can be used for search box, and for UI elements like ones in Wikidata. It should be a continuation of cirrus-suggest API currently used for testing. It should also allow control over which fields are used for suggestions and allow passing context. See: https://www.elastic.co/guide/en/elasticsearch/reference/current/suggester-context.html