Authenticate to the Suprema BioStar 2 API and retrieve a session for subsequent user/device calls

Steps

1. Call POST /api/login on your BioStar 2 server with a JSON body of the form {"User": {"login_id": "...", "password": "..."}}
2. On a successful response, read the bs-session-id value from the response headers rather than the body
3. Attach that value as the bs-session-id header on every subsequent API call (e.g. GET /users to list users, or credential/device endpoints) to authorize the request
4. Use standard HTTP verbs (GET/POST/PUT/DELETE) against BioStar 2's JSON REST resources such as /users for user creation and management
5. Re-authenticate via /api/login again once the session expires or calls start returning auth errors