Implement the OCPP 2.0.1 TransactionEvent lifecycle for charge-point-to-CSMS session and metering reporting

Steps

1. Adopt OCPP 2.0.1's unified TransactionEvent message instead of 1.6's separate StartTransaction/StopTransaction/MeterValues calls
2. Send TransactionEvent with eventType Started, Updated, or Ended over the OCPP WebSocket connection to the CSMS
3. Populate triggerReason (e.g. CablePluggedIn, Authorized, MeterValuePeriodic, EVDeparted) to explain why the event fired
4. Embed meterValue arrays (e.g. energy.active.import.register, power, current, SoC) directly inside the TransactionEvent payload
5. Have the CSMS return idTokenInfo authorization status on the Started event before energy delivery proceeds