Authenticate with the project44 API using OAuth 2.0 client credentials and manage token refresh for continuous shipment visibility calls

Steps

1. Register an application in the project44 developer portal to obtain a client ID and client secret for your environment (sandbox or production).
2. POST to the project44 OAuth token endpoint with grant_type=client_credentials, client_id, and client_secret; receive an access_token and expires_in value.
3. Store the token in memory with an expiry timestamp; wrap every outbound API call to check if the token is within a safe refresh window (e.g., 60 seconds before expiry) and re-fetch before the call.
4. Include the token as a Bearer value in the Authorization header on all subsequent requests to the project44 Visibility, Capacity, or Shipment APIs.
5. Handle 401 responses by immediately discarding the cached token, re-authenticating, and retrying the failed request exactly once to cover race conditions at token boundary.