Live2SessionClient

Initializes a BLive 2.0 SSAI session by POSTing to the source manifest URL. Returns the session's manifest URL (with session_id for playback) and tracking URL.

The manifest URL MUST be used for playback so the tracking API can associate ad avails with this viewer session.

Note: Uses HttpURLConnection directly because the SDK's HttpService does not support POST requests with a JSON body.