Attribute Macro helper 

#[helper]

Marks a struct as a controller helper. Generates a [doido_controller::Helper] implementation that carries the snake_case helper name (PostsHelper → "posts_helper"), matching the app/helpers/<name>_helper.rs convention. Import the helper in controllers and call its associated functions.

#[helper]
pub struct PostsHelper;

impl PostsHelper {
    pub fn format_title(title: &str) -> String { title.to_uppercase() }
}