Execute multiple contract invocations with explicit auth checking
This version explicitly calls require_auth() for transfer operations to ensure all sender addresses are properly authorized in the auth tree.
Arguments:
fn exec(
env: soroban_sdk::Env,
caller: soroban_sdk::Address,
invocations: soroban_sdk::Vec<
(
soroban_sdk::Address,
soroban_sdk::Symbol,
soroban_sdk::Vec,
bool,
),
>,
) -> soroban_sdk::Vec