curl --request POST \
  --url https://api.charp.ai/auth/refresh \
  --header 'Content-Type: application/json' \
  --data '{
  "refresh_token": "<string>"
}'

{
  "access_token": "<string>",
  "token_type": "<string>",
  "expires_in": 123,
  "refresh_token": "<string>"
}