nomenclature: unit vs units

[CagtayFabry]

Since we implemented our own quantity schema in #519 we no longer have to follow the asdf schema which would allow us to rename the unit field of the quantity

In general two options come to mind: unit oder units
I think it would be very good to decide on one of these options and use that consistently throughout weldx

Maybe we should look into other fields what is most common. I know that pint-xarray stores unit information under the units key but not sure if that is actually defined in the CF-conventions

Any preferences? please discuss

[vhirtham]

Not sure here but I would stick to the plural form -> units

[CagtayFabry]

a quick search for unit:\n gave the following results where we use that property name in schemas:

• quantity
• signal
• time_series
• variable

So I don't think it is too bad

if we want to rename to units we would have to provide the back compatibility for these schemas and we should certainly do that in the 0.5 release since otherwise the code will just get messier

I guess in these cases we only need a simple

if "units" in node:
  _units = U_(node["units"])
else:
  _units = U_(node["unit"])

[vhirtham]

I will turn this discussion into an issue and add it to the 0.5.0 milestone, okay?

[CagtayFabry]

I'll quickly draft the initial changes