ActiveRecord is not allowing :tax_applicable_on to set a string but is

demanding a date.

Error parsing XML: tax_applicable_on: invalid date for class
Quickbooks::Model::JournalEntryLineDetail

Most likely AR is overriding '_on' suffix setters. Provide an
alternate xml_accessor :tax_applicable for these cases but I didn't
research in depth.

Also see:
https://intuitpartnerplatform.lc.intuit.com/questions/980169-i-got-this-error-when-trying-to-add-tax_applicable_on-field-i-set-the-above-filed-to-credit-but-it-says-its-some-date-class

cc: @markrickert