Custodial multi-step route. See docs/INTEGRATION.md for ABI,
fee_position, arg_refs, and bridge-route semantics.
fn route(
env: soroban_sdk::Env,
user: soroban_sdk::Address,
swap_id: soroban_sdk::BytesN<16>,
input_token: soroban_sdk::Address,
input_amount: u128,
output_token: Option,
steps: soroban_sdk::Vec,
affiliate_fees: soroban_sdk::Vec,
fee_position: u32,
receiver: Option,
) -> u128 Permissionless instance-TTL keep-alive.
fn bump_ttl(env: soroban_sdk::Env)