curl --request POST \
  --url https://logintest.clearline.me/connect/token \
  --header 'Authorization: <authorization>' \
  --header 'Content-Type: application/x-www-form-urlencoded' \
  --data grant_type=authorization_code \
  --data code=authorization_code_from_callback \
  --data redirect_uri=clover://auth-callback \
  --data code_verifier=original_code_verifier_string

{
  "access_token": "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9...",
  "token_type": "Bearer",
  "expires_in": 3600,
  "refresh_token": "df8a2f3e...",
  "scope": "clearline_api"
}