Macro require 

macro_rules! require {
    ($condition:expr, $message:expr $(,)?) => { ... };
    ($condition:expr, $format:expr, $($arg:expr),+ $(,)?) => { ... };
}

Validates a business rule condition and returns early with CommandError::BusinessRuleViolation when the condition is false.

Designed for command handlers (or any function returning Result<_, CommandError>) so domain invariants stay close to the logic without verbose boilerplate.

Examples

With a literal message:

require!(balance >= amount, "Insufficient funds");

With a formatted message:

require!(
    balance >= amount,
    "Insufficient: have {}, need {}",
    balance,
    amount,
);