General dataframes join transformer helper class

[FarBo]

At the moment, we have the following join transfomer:
https://github.com/atc-net/atc-dataplatform/blob/main/src/atc/transformers/join_dataframes_transformer.py

The problem is this is non-consuming join, and also it asks for strings for dataframes, which makes it unuseable for joining two dataframes as input arguments for the class.
The question is, should we extend this module with another more general class?
@LauJohansson
@sjkp