Macro define_error_codes 

macro_rules! define_error_codes {
    ($namespace:expr, $category:expr => { $( $name:ident = ($code:expr, $impact:expr) ),+ $(,)? }) => { ... };
}

Define multiple error codes within the same namespace.

Example

define_error_codes! {
    &namespaces::CFG, OperationCategory::Configuration => {
        CFG_PARSE_FAILED = (100, 350),
        CFG_VALIDATION_FAILED = (101, 250),
    }
}