Implement the new Search-A-Licious ElasticSearch search endpoint

[teolemon]

Why - Problem description

• As part of the search revamp project, we will be deploying a new Elasticsearch endpoint at https://search.openfoodfacts.org/docs#/
• It will be OpenAPI compatible so we can generate a base Flutter SDK automatically that we can draw from here.
• We will also be upgrading the classic product-opener search to use this backend in the background (with an unchanged API vs what we've already implemented), so we should not deprecate immediately classic search.
• We should also implement direct calls to the Elasticsearch endpoint. This will pave the way for a fuller search implementation in Smoothie.

URL of the doc

https://search.openfoodfacts.org/docs#/

Routes

• /document/{identifier}
• /autocomplete

Schemas

• ErrorSearchResponseExpand allobject
• HTTPValidationErrorExpand allobject
• SearchResponseDebugExpand allobject
• SearchResponseErrorExpand allobject
• SuccessSearchResponseExpand allobject
• ValidationErrorExpand allobject

Sub-issues already opened

Related issue in the official mobile app

• 🔍 Search (tracker) smooth-app#991

[monsieurtanuki]

My first tests show some problems/questions.

parameter discrepancies

In the current version

1. we pass the country as a parameter
   => shouldn't we do so Elastic Search?
2. we pass app_name as a parameter
   => shouldn't we do so Elastic Search?
3. we pass the user name in the http header
   => shouldn't we do so Elastic Search?

product structure discrepancies

In the current version
4. the "brands" product field is a comma-separated String, and in Elastic Search it's a List<String>.
=> it probably means that we need a specific new Product class.