Add support for passing query parameters to StockBalance

[martenw]

Fix for #343

[adamelfstrom]

Hi, thank you for contributing.

While this does solve the specific issue of missing parameters for StockBalance, the other endpoint added in the referenced PR, StockPoint has the same issue which also needs to be addressed.
I also don't think this is the preferred solution.

Imo, this issue should instead be addressed by adding a search parameter class like we do for all the non-warehouse endpoints. So instead of passing in several parameters to the QueryAsync function, you would pass in an instance of e.g. StockPointSearch where the parameters are defined. Since the search class would inherit from BaseSearch, the limit and offset parameters would be available by default.

[adamelfstrom]

Also it seems the testing account finally stopped working, so that also needs fixing first...

[martenw]

Agree, this is just a fix that makes the endpoint useable but it is probably not a long-term fix. I used this implementation in my project just to make it work.