So HA can show the full payable: net = import - export = Total Payable, with
both entities staying monotonic-positive (no negative-value/reset pitfalls).
- import_cost_total = SUM(import_cost) + days*(network_fee+management_fee)/30
- export_revenue_total = SUM(export_revenue) + days*heffingskorting/365
(days = calendar days since the active version's effective_from, incl. today)
- state_class total_increasing -> total (monetary-compatible; values still only
increase). device_class/key/names: key unchanged, names clarified.
- buy/sell_price_now and DeviceInfo untouched. Decimal money math. Tests added.
The energy-cost device has only sensors (no online/offline heartbeat), but the
discovery config still declared an availability topic that nothing ever publishes
'online' to — so Home Assistant marked every energy-cost entity 'unavailable'
even though the state topic was being published (visible in MQTT Explorer).
- DeviceInfo gains provides_availability (default True, keeps Modbus behavior).
- _energy_cost_provider sets provides_availability=False.
- build_discovery_payload only emits availability/availability_mode for devices
that publish a heartbeat; HA treats the rest as always-available.
- Test asserts energy-cost configs omit availability.
tliu93