A single fee line on a Stripe BalanceTransaction.
Reconciliation code typically filters by type to extract platform fees:
application_fees =
Enum.filter(bt.fee_details, &(&1.type == "application_fee"))Stripe's known type enum values include "application_fee",
"stripe_fee", "payment_method_passthrough_fee", "tax", and
"withheld_tax". The field stays typed as String.t() to remain
forward-compatible with new fee categories.