pub fn enum_attribute<P: AsRef<str>, A: AsRef<str>>(mut self, path: P, attribute: A) -> Self {
        self.enum_attributes
            .push((path.as_ref().to_string(), attribute.as_ref().to_string()));
        self
    }
Add additional attribute to matched enums.

Passed directly to `prost_build::Config.enum_attribute`.
tonic-build/src/prost.rs