POST /api/v1/sub-merchant

{
  "name": "Ma Boutique",
  "commercialName": "Ma Boutique SN",
  "countries": ["SN", "CI"],
  "description": "Boutique en ligne",
  "legalName": "Ma Boutique SARL",
  "businessActivity": "E-commerce",
  "managerName": "John Doe",
  "websiteURL": "https://maboutique.com",
  "phoneNumber": "+221771234567",
  "city": "Dakar",
  "address": "123 Rue du Commerce",
  "zipcode": "12000"
}

{
  "success": true,
  "message": "Sub-merchant created successfully",
  "data": {
    "subMerchantId": "sm-7f4a9940c621",
    "name": "Ma Boutique",
    "commercialName": "Ma Boutique SN",
    "countries": ["SN", "CI"],
    "isActive": true,
    "isDefault": false,
    "CREATED_AT": "2026-03-15T03:47:32.000Z"
  }
}