private static Optional<ValidationEvent> validateStringProperty(
            BiFunction<FromSourceLocation, String, ValidationEvent> emitter,
            Map<Identifier, Literal> properties,
            Identifier propertyName
    ) {
        return validatePropertyType(emitter,
                properties.get(propertyName),
                propertyName,
                Literal::asStringLiteral,
                "a string");
    }
Returns if a given auth scheme is equivalent to {@code aws.auth#sigv4a}.

@param authScheme name of the auth scheme.
@return whether the auth scheme is equivalent to {@code aws.auth#sigv4a}.
smithy-aws-endpoints/src/main/java/software/amazon/smithy/rulesengine/aws/language/functions/EndpointAuthUtils.java