public Optional<String> getCredentials() {
        return Optional.ofNullable(credentials);
    }
Gets the credentials required for the integration, if any.

<p>For AWS integrations, three options are available. To specify an
IAM Role for API Gateway to assume, use the role's
Amazon Resource Name (ARN). To require that the caller's identity
be passed through from the request, specify the string
{@code arn:aws:iam::*:user/*}. Resource-based permissions are used if
no credentials are provided.

@return Returns the optionally present credentials.
smithy-aws-apigateway-traits/src/main/java/software/amazon/smithy/aws/apigateway/traits/IntegrationTrait.java