On SubscriptionOrders, it is possible to add OrderFeeCategories on CreateSubscriptionOrders, and update OrderFeeCategories on UpdateSubscriptionOrders.
The FeeCategories to use must be connected to the instrument by its FeeCategoryGroup, and this must be done in the GUI.
The values to set, for each OrderFeeCategory, is Key and Amount. If the FeeCategory to use is configured to draw fee in percentage, the value for Amount should
be set as a percentage value, that is 0.15 equals 15%. If the FeeCategory is configured to draw fee in amount, the value should be set as an amount.
When updating FeeCategories through UpdateSubscriptionOrder, amount on existing categories(found by the key) will be updated. If a FeeCategory is to be removed, just set the amount to 0
for that FeeCategory. If a new category is to be added, add the new category. If the category exists in the FeeCategoryGroup for the instrument, it will be added. If it does not, an error will be returned.