Adding `cos_solar_zenith_angle_integrated` function from earthkit-meteo

[da-ewanp]

Is your feature request related to a problem? Please describe.

It would be great to have the cos_solar_zenith_angle_integrated function from earthkit.meteo.solar included alongside the other relevant functions in climetlab/sources/constants.py. So that this was available for the constants in the anemoi-datasets zarr creation. 🙏

Describe the solution you'd like

Including cos_solar_zenith_angle_integrated function from earthkit.meteo.solar in climetlab/sources/constants.py. This function requires both a start and end date time to generate the integrated cos_sza. This would most likely be using the freq parameter from anemoi-datasets, so that start_date = date - freq and end_date = date.

Describe alternatives you've considered

No response

Additional context

I am creating some land surface datasets using anemoi-datasets and require some additional variables

Organisation

ECMWF