Authenticate with the Bullhorn REST API and create a new Candidate record

Steps

1. Run the OAuth2 authorization-code flow against Bullhorn's OAuth token endpoint to obtain an access token and refresh token
2. Call the REST login endpoint with the access token to receive a session token plus a swimlane-specific REST base URL
3. Send the session token on each request as documented (query string, cookie, or header)
4. Create the candidate by sending the entity-create request to the Candidate entity endpoint with fields such as first name, last name, and email
5. Capture the returned entity ID to confirm the record was created
6. On an authentication-expired response, use the refresh token to obtain a new session rather than repeating the full authorization flow