Disable connections/communication from "Rejected" stations

[goekay]

If the station has registration_status value Rejected,

• SOAP messages should not be allowed/processed (seems the be the case already, for double checking)
• WebSocket connection attempts should be rejected

RegistrationStatus from ocpp spec:

[goekay]

relates to an earlier ticket.

initial idea and impl was found to be too strict, and then i relaxed it. i want to open this behaviour to discussion again, but only for Rejected status.

reason and motivation: if i want to block/reject a station, i can only change its status. then i am at the mercy of the station implementation that it will close the connection and not re-attempt after BootNotification response with Rejected status. as a result, we might have many dangling open websocket connections (relevant for server resources and DoS loops). the only option to prevent this would be to delete the station from my system upon which i will lose all its data. Rejected was there in pre-websocket era of OCPP as well, where it made more sense.