fn initialize(env: soroban_sdk::Env)
fn get_referrer(
env: soroban_sdk::Env,
referee: soroban_sdk::Address,
) -> Option
fn record_volume(env: soroban_sdk::Env, user: soroban_sdk::Address, amount: i128)
fn get_fee_discount(env: soroban_sdk::Env, user: soroban_sdk::Address) -> u32
fn register_referral(
env: soroban_sdk::Env,
referrer: soroban_sdk::Address,
referee: soroban_sdk::Address,
)