Macro impl_standard_methods 

macro_rules! impl_standard_methods {
    (
        $Registry:ty,
        $Entry:ty,
        $id_field:ident,
        $key_field:ident,
        $allow_registering:ident
        $(, $duplicate_key_error:literal)?
    ) => { ... };
}

Implements the default register and iter methods in the registries.

An optional final error format enables duplicate-key rejection for registries whose entries carry behavior that must remain tied to their registered identity.