pub fn with_violation(subject: impl Into<String>, description: impl Into<String>) -> Self {
        QuotaFailure {
            violations: vec![QuotaViolation {
                subject: subject.into(),
                description: description.into(),
            }],
        }
    }
Creates a new [`QuotaFailure`] struct with a single [`QuotaViolation`]
in `violations`.
tonic-types/src/richer_error/std_messages/quota_failure.rs