public virtual IEnumerable <string> GetValidationErrors()
        {
            if (Authority.IsMissing() && TokenEndpoint.IsMissing())
            {
                yield return($"You must either set {nameof(Authority)} or {nameof(TokenEndpoint)}.");
            }

            if (ClientId.IsMissing())
            {
                yield return($"You must set {nameof(ClientId)}.");
            }

            if (ClientSecret.IsMissing())
            {
                yield return($"You must set {nameof(ClientSecret)}.");
            }

            if (AuthorityHttpClientName.IsMissing())
            {
                yield return($"You must set {nameof(AuthorityHttpClientName)}.");
            }

            if (Events == null)
            {
                yield return($"You must set {nameof(Events)}.");
            }
        }