total revenue for a given merchant

[abreaux26]

• This endpoint should return the total revenue for a single merchant.
• The URI should follow this pattern: GET /api/v1/revenue/merchants/:id
• Example JSON response for GET /api/v1/revenue/merchants/1

{
  "data": {
    "id": "42",
    "type": "merchant_revenue",
    "attributes": {
      "revenue"  : 532613.9800000001
    }
  }
}