fn set_rule(
env: soroban_sdk::Env,
user: soroban_sdk::Address,
token: soroban_sdk::Address,
max_amount: i128,
merchant_whitelist: soroban_sdk::Address,
expires_at: u64,
)fn delegated_payment(
env: soroban_sdk::Env,
user: soroban_sdk::Address,
recipient: soroban_sdk::Address,
amount: i128,
)