Remove trailing whitespaces

[phackstock]

It might be a good idea to remove training white spaces from the dimensions of model, scenario, variable and unit.
The fact that we currently don't do this causes some overhead in fixing these issues that could be fixed automatically.

[danielhuppmann]

Nice idea, and we already do this for codelists...

nomenclature/nomenclature/codelist.py

Line 57 in 48dc9e1

def check_end_whitespace(

Question is whether that should be used on columns that are not explicitly checked as part of DataStructureDefinition.validate().

[phackstock]

Good question, maybe this should be part of pyam anyway. Just as part of the reading in process stripping all the trailing whitespace of all values in all columns.
Then we wouldn't need to even think about where to add it. We could just assume that all the values inside a pyam.IamDataFrame are clean.