pub enum ServiceError {
    #[display(fmt = "internal server error")]
    InternalServerError,

    // ...

    #[display(fmt = "Password too short")]
    PasswordTooShort,
    #[display(fmt = "Username too long")]
    PasswordTooLong,
    #[display(fmt = "Passwords don't match")]
    PasswordsDontMatch,

    // ...

pub enum ServiceError {
    #[display(fmt = "internal server error")]
    InternalServerError,

    // ...

    #[display(fmt = "Password too short")]
    PasswordTooShort,
    #[display(fmt = "Password too long")]
    PasswordTooLong,
    #[display(fmt = "Passwords don't match")]
    PasswordsDontMatch,

    // ...