curl --request POST \
  --url https://api.opx.co/partners/v1/beneficiaries \
  --header 'Content-Type: application/json' \
  --data '{
  "firstname": "<string>",
  "lastname": "<string>",
  "company_name": "<string>",
  "siren": "<string>",
  "siret": "<string>",
  "address": "<string>",
  "city": "<string>",
  "zipcode": "<string>",
  "country": "<string>",
  "mobile_phone": "<string>",
  "phone": "<string>",
  "email": "jsmith@example.com",
  "convention_id": 123
}'

{
  "data": {
    "id": 123,
    "firstname": "<string>",
    "lastname": "<string>",
    "company_name": "<string>",
    "siren": "<string>",
    "siret": "<string>",
    "address": "<string>",
    "city": "<string>",
    "zipcode": "<string>",
    "country": "<string>",
    "mobile_phone": "<string>",
    "phone": "<string>",
    "email": "<string>"
  }
}