Changes to expense sales tax reporting

Hi all,

We’re about to change how we report sales tax for expenses in order to
match the desktop app better and fix a bug. Please note that this does not
affect the sales_tax_value attribute, which is an amount calculated from
either the sales_tax_rate, or the manual_sales_tax_amount on the expense.
The fix we are pushing changes only how the sales_tax_rate and
manual_sales_tax_amount are reported by the API, so if you base your
calculations on sales_tax_value, no changes are needed.

Currently, if an expense has a manual sales tax amount set (e.g. £12.5), it
is always returned, even if a sales tax rate is set to override it (e.g.
20% VAT). We will change this behaviour so if a sales tax rate is set, the
sales_tax_rate attribute will be present on the expense, otherwise
manual_sales_tax_amount will.

We expect this change to go live next Monday. If you have any code which
relies on manual_sales_tax_amount always being present, please update it