public Optional<String> getConnectionId() {
        return Optional.ofNullable(connectionId);
    }
Gets the ID of a VpcLink when using a private integration.

@return Returns the optionally present connection ID.
@see <a href="https://docs.aws.amazon.com/apigateway/api-reference/resource/vpc-link/">VPC Link</a>
smithy-aws-apigateway-traits/src/main/java/software/amazon/smithy/aws/apigateway/traits/IntegrationTrait.java