🪠 Plumb through notify_charging_limit as a NOP

[shankari]

So that we can finish testing the EVerest changes in EVerest/everest-demo#101 end-to-end

I have not yet plumbed through the changes to clear_charging_limit but they should be fairly simple, and I can leave them as an exercise for @Abby-Wheelis

Outline of changes:

• add notify_charging_limit to the CallMap, and have it redirect to the notify_charging_limit_handler
• add a handler for the notify_charging_limit
• add classes for the request and response that we can use in the handler

Testing done:
Without this change:
EVerest/everest-demo#101 (comment)

With this change:

2025-01-27 02:36:16.234166 [INFO] ocpp:OCPP201     :: Received internal set_charging_limit: for 1 with purpose 15
2025-01-27 02:36:16.234471 [INFO] ocpp:OCPP201     :: SHANKARI: Invoking validate_and_add_profile with 1 and source EMS
2025-01-27 02:36:16.234598 [INFO] evse_manager_1:  :: set_max_current (14, 2025-01-27 02:36:26.094000000) called
2025-01-27 02:36:16.234517 [INFO] ocpp:OCPP201     :: SHANKARI: invoked validate_profile for evse_id: 1 and profile {
    "chargingProfileKind": "Absolute",
    "chargingProfilePurpose": "ChargingStationExternalConstraints",
    "chargingSchedule": [
        {
            "chargingRateUnit": "A",
            "chargingSchedulePeriod": [
                {
                    "limit": 15.0,
                    "startPeriod": 0
                }
            ],
            "duration": 86400,
            "id": 0,
            "startSchedule": "2025-01-27T02:36:16.234Z"
        }
    ],
    "id": 398,
    "stackLevel": 10
}
2025-01-27 02:36:16.234902 [INFO] ocpp:OCPP201     :: SHANKARI: after validating file request source
2025-01-27 02:36:16.234926 [INFO] ocpp:OCPP201     :: SHANKARI: after validating conflicting external constraints
2025-01-27 02:36:16.235939 [INFO] ocpp:OCPP201     :: SHANKARI: before validating by purpose
2025-01-27 02:36:16.235974 [INFO] ocpp:OCPP201     :: SHANKARI: should return valid here!
2025-01-27 02:36:16.235986 [INFO] ocpp:OCPP201     :: SHANKARI: result for 1 is Valid
2025-01-27 02:36:16.236010 [INFO] ocpp:OCPP201     :: SHANKARI: Modifying database
2025-01-27 02:36:16.243501 [INFO] ocpp:OCPP201     :: Returning from on_charging_limit_set with 1 and status Accepted

{"type":2,"action":"NotifyChargingLimit","id":"feda7835-c7d5-4717-8df6-79cdc5b17e9c","request":{"chargingLimit":{"chargingLimitSource":"EMS"},"chargingSchedule":[{"chargingRateUnit":"A","chargingSchedulePeriod":[{"limit":15.0,"startPeriod":0}],"duration":86400,"id":0,"startSchedule":"2025-01-27T02:36:16.234Z"}],"evseId":1}}

{"type":3,"action":"NotifyChargingLimit","id":"feda7835-c7d5-4717-8df6-79cdc5b17e9c","response":{}}