curl --include \
     --request POST \
     --header "Content-Type: application/json; charset=utf-8" \
     --header "Authorization: Basic YOUR_REST_API_KEY" \
     --data-binary "{\"app_id\": \"YOUR_APP_ID\",
\"contents\": {\"en\": \"English Message\"},
\"headings\": {\"en\": \"English Title\"},
\"included_segments\": [\"Subscribed Users\"]}" \
     https://onesignal.com/api/v1/notifications