Add support for the `conditions` filters variables to apply nested conditions

[ciphrd]

Add support for the conditions field:

{
  "filters": {
    "operator": "OR",
    "conditions": [
      {
        "operator": "AND",
        "price_gte": "1000000",
        "cancelledAt_exist": true
      },
      {
        "operator": "AND",
        "price_lte": "500000",
        "cancelledAt_exist": true
      }
    ]
  }
}

It should compose AND and OR operations.

• requires Add support for the operator field in the Filters #19