Macro operation_enum 

macro_rules! operation_enum {
    (
        $(#[$meta:meta])*
        $vis:vis enum $name:ident {
            $($(#[$variant_meta:meta])* $variant:ident($inner:ty),)+
        }
    ) => { ... };
}

Define the enum that wraps the operations of each resource.

Each variant holds the operation type of one resource. The enum gets a Display that shows the inner operation and a From for each inner type.

#[derive(Clone, Debug, Eq, PartialEq)]
pub struct Rename;

impl std::fmt::Display for Rename {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.write_str("repository")
    }
}

ephemeris_forge::operation_enum! {
    /// One write.
    pub enum Operation {
        /// A write to the repository.
        Repository(Rename),
    }
}

assert_eq!(Operation::from(Rename).to_string(), "repository");