Generating an Access Token

curl -X POST https://auth-sandbox.fexpayments.com/realms/payment-platform/protocol/openid-connect/token \
  -H "Content-Type: application/x-www-form-urlencoded" \
  -d "grant_type=client_credentials" \
  -d "client_id=merchant-a1b2c3d4-..." \
  -d "client_secret=xxxxxxxxxxxxxxxx"

{
  "access_token": "eyJhbGciOiJSUzI1NiIs...",
  "expires_in": 300,
  "token_type": "Bearer"
}

if token is None or token_expires_at < now() + 30s:
    token = fetch_new_token(client_id, client_secret)
    token_expires_at = now() + token.expires_in