find a quantity of merchants sorted by descending revenue

[abreaux26]

• This endpoint should return a variable number of merchants ranked by total revenue.
• The URI should follow this pattern: GET /api/v1/merchants/revenue?quantity=x
• where x is the number of merchants to be returned. The quantity parameter is required, and should return an error if it is missing or if it is not an integer greater than 0.
• Example JSON response for GET /api/v1/merchants/most_revenue?quantity=2

{
  "data": [
    {
      "id": "1",
      "type": "merchant_name_revenue",
      "attributes": {
        "name": "Turing School",
        "revenue": 512.256128
      }
    },
    {
      "id": "4",
      "type": "merchant_name_revenue",
      "attributes": {
        "name": "Ring World",
        "revenue": 245.130001
      }
    }
  ]
}