zeebe credentials sourcing

creds.java

   if (accessKey == null) {
      logger.info("Creating Lambda client without credentials the container will use task IAM role ");
      Regions region = Regions.fromName(this.region);
      AWSLambdaClientBuilder builder = AWSLambdaClientBuilder.standard()
              .withRegion(region);
      client = builder.build();
    } else {
      logger.info("Creating Lambda client with provided access and secret key");
      Regions region = Regions.fromName(this.region);
      BasicAWSCredentials credentials = new BasicAWSCredentials(accessKey, secret);
      AWSLambdaClientBuilder builder = AWSLambdaClientBuilder.standard().withCredentials(new AWSStaticCredentialsProvider(credentials)).withRegion(region);
      client = builder.build();
    }
    return client;