Convert certain objects to scientific metadata entries

[jl-wynen]

From a discussion with @nvaytet:

The scientific metadata looks like
{'value': 1609.91, 'unit': 'uAh', 'valueSI': 1609.91, 'unitSI': 'uAh'}
If this is the standard we should use, when populating this for a derived data, it would be super if I could add in there directly some scipp variables. Right now, if I do derived.meta['background_level'] = sc.scalar(300, unit=counts) it has my scipp variable locally, but I am guessing that when I upload to scicat, this won't work, or be converted to a string?

Jan-Lukas Wynen
I'd prefer to not depend on Scipp in Scitacean.
Also, this is only the ess convention. Other facilities use more free form dicts.

Jan-Lukas Wynen
Also also, valueSI and unitSI are set by SciCat, you only need to specify value and unit.

Neil Vaytet
Can we make a translator in the setitem that converts a scipp variable to to the value/unit dict? You wouldn't necessarily have to depend on scipp to check the type, you could check if it is not a dict, and then see if it hasattr('unit')?

Jan-Lukas Wynen
Could do. So it could check if the arg implements

class MetaValue(Protocol):
  @property
  def value(self): ...

  @property
  def unit(self): ...

But still, this would be ESS-specific.