List customers

curl --request POST \
  --url https://api.etherfuse.com/ramp/customers \
  --header 'Content-Type: application/json' \
  --header 'X-API-Key: <api-key>' \
  --data '{
  "page_size": 10,
  "page_number": 0
}'

{
  "items": [],
  "total_items": 0,
  "page_size": 10,
  "page_number": 0,
  "total_pages": 0
}