Function default_roles 

pub fn default_roles() -> HashMap<String, RolePermissions>

Create the built-in role map used when AdminConfig::roles is unset.

Extend a role before passing the map to the plugin:

use alibi_plugins::admin::{AdminPlugin, admin_role, default_roles};

let mut roles = default_roles();
roles.insert("admin".into(), admin_role().allow("job", ["read", "manage"]));
let plugin = AdminPlugin::new().roles(roles);