feat: 620 - Elastic Search autocomplete for categories

[monsieurtanuki]

What

• First use of the Elastic Search API: autocomplete for categories in TEST env.
• TODO in other PRs
  • access to PROD env (so far, only TEST env works)
  • other fuzziness levels (so far, just none)
  • other taxonomy names (so far, just category)

Part of

• Use the new ElasticSearch endpoint to provide search as you type product suggestions #620

Files

New files:

• api_search_test.dart: Tests around the Elastic Search API.
• autocomplete_search_result.dart: Result of an autocomplete search on the Elastic Search API.
• autocomplete_search_result.g.dart: generated
• autocomplete_single_result.dart: Single item result of an autocomplete search on the Elastic Search API.
• autocomplete_single_result.g.dart: generated
• fuzziness_level.dart: Fuzziness Level for Elastic Search API.
• open_food_search_api_client.dart: Client calls of the Open Food Facts Elastic Search API.
• taxonomy_name.dart: Taxonomy Name for Elastic Search API.

Impacted files:

• openfoodfacts.dart: exported the new 5 files.
• uri_helper.dart: added a forcedHost parameter in order to deal with alternative subdomains like search for Elastic Search

[g123k]

Apart from your code, I was wondering whether we shouldn't create an experimental part in the SDK.
That would make it possible to include this PR, but also the one for pricing.
The idea would be to say: you can test, but at any time the API can change or disappear.

[raphael0202]

One of the advantage of this API is the support for brand, is it something you plan to add as well?

[monsieurtanuki]

Thank you @raphael0202 for your review!

As I wrote, there are things that I planned to code but I'm blocked and you may be helpful:

• could you provide a list to all (or many) "taxonomy name"s, or a way to get them?
• could you provide a list of values and meanings of fuzziness levels?
• any idea when the PROD env will be available?

[raphael0202]

could you provide a list to all (or many) "taxonomy name"s, or a way to get them?

Yes, it's available here! If you need more, it's easy to index new ones
https://github.com/openfoodfacts/search-a-licious/blob/main/data/config/openfoodfacts.yml#L132

could you provide a list of values and meanings of fuzziness levels?

Fuziness is an int, it's the maximum allowed levenshtein distance (=number of edits): https://www.elastic.co/guide/en/elasticsearch/reference/current/common-options.html#fuzziness

any idea when the PROD env will be available?

We plan to install search-a-licious on off1, the server that was used so far to host Product Opener (the migrations went smoothly yesterday 🎉). We need to perform software and hardware upgrades, it's expected to be ready in ~3 weeks.