curl --request POST \
  --url https://api.dirtroad.dev/tools/string-utils/count-occurences \
  --header 'Content-Type: application/json' \
  --header 'X-Payment: <api-key>' \
  --data '{
  "str": "<string>",
  "substring": "<string>",
  "caseSensitive": false
}'

{
  "str": "<string>",
  "substring": "<string>",
  "caseSensitive": true,
  "result": 123
}