curl --request POST \
  --url https://management.stytch.com/pwa/v3/projects/:project_slug/environments/:environment_slug/allowed_country_codes/sms \
  --header 'Authorization: Basic <encoded-value>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "country_codes": [
    "<string>"
  ]
}
'

{
  "request_id": "<string>",
  "country_codes": [
    "<string>"
  ],
  "status_code": 123
}