add export peak boolean sensor

[tomarigr]

Describe the feature

Currently, there is an export off-peak boolean sensor but that being off doesn't mean that it's now export peak so it can't be relied upon.
As an example, the export peak start for flux tariff is many hours apart from export off-peak.

Manual helper template sensors can be created but they won't update automatically if flux time has changed.

Expected behaviour

octopus_energy_electricity_XXXXXX_XXXX_export_peak turns on for as long as tariff's highest export rate is active (eg 16:00 to 19:00 in flux)

Use Case

can be used to discharge/feed-in when export rates are at the highest level.

Confirmation

• By submitting this feature request, you agree that you have read the documentation and confirmed it does not already exist
• I am willing/able to help contribute to the solution of this feature

[BottlecapDave]

Thank you for suggesting. I'm not sure when I'll get to it unless more demand is requested. But in case anyone wants to get to it before me

• Add new sensor with same attributes as current off_peak sensor
• Should only be available for tariffs with 2 or 3 unique rates (see cost tracker custom_components\octopus_energy\cost_tracker\cost_tracker_month.py with how this should be done around the peak types)
• Should probably refactor the existing functions for the off_peak sensor to work for both off_peak and peak (e.g. taking a target rate as an input parameter?)
• Update docs
• Include unit tests for any new functions