Add support for the `operator` field in the Filters

[ciphrd]

Any filter object in the variables supports the operator parameter.
It should change the behavior of the WHERE sql conditions and should either perform a OR or AND query based on the filter.

Currently, this filter is ignored and only AND operations are performed.

{
  "filters": {
    "type_in": [
      "MINTED",
      "MINTED_FROM"
    ],
    "operator": "OR"
  }
}

Filters are applied on a case-by-case basis and every endpoint should be examined to check it they implement filters.
This may require a general refacto to apply filters in a more generic fashion.