Optional filtering

[Kerollmops]

Optional filters divide your records into two sets: the results matching the optional filter and those not. These filters can be used for promoting/boosting/pinning products. The higher the score, the higher the product.

Here is a basic version inspired by Algolia:

{
  "q": "phone",
  "optionalFilters": [
      "brand:Apple<score=3>",
      "brand:Samsung<score=2>",
      "brand:-Huawei"
  ]
}

This above filter syntax is debatable as it implies changing the syntax a bit and may be challenging to understand. Can we keep the current syntax and keep the same features? Note that this syntax is used in the main filter scoring Algolia feature: #649.