Reservation Handling for no specific EVSE / connector#0

[Pietfried]

The reservation handler in the Auth module does currently not support reservations of connector 0 (reservations for the whole charging station and not for a specific EVSE/connector).

The goal of this issue is to implement support so that the requirement of OCPP1.6 and OCPP2.0.1 for this use case is fullfiled:

H01.FR.07 of OCPP 2.0.1 Edition 2 FINAL, 2022-12-15:

When the Charging Station has Accepted a ReserveNowRequest without evseId
The Charging Station SHALL make sure that at any time during the validity of the reservation, one EVSE remains available for the reserved IdTokenType.

OCPP1.6 edition 2 FINAL, 2017-09-28:

If the connectorId in the reservation request is 0, then the Charge Point SHALL NOT reserve a specific connector, but SHALL make sure that at any time during the validity of the reservation, one connector remains available for the reserved idTag