[BUG] AWS Neptune to OpenSearch Lambda Poller fails with exception: 'Action/metadata line [1] contains an unknown parameter [_type]'

[mcuervoe]

Describe the bug
The lambda created to ingest Neptune data into OpenSearch fails with exception ''Action/metadata line [1] contains an unknown parameter [_type]' when the OpenSearch engine was migrated from ElasticSearch 7.9 to OpenSearch 2.5

To Reproduce
Steps to reproduce the behavior:

1. Create an AWS Neptune Instance (version 1.2)
2. Create an OpenSearch Instance (version 2.5)
3. Install Amazon Neptune-to-OpenSearch replication setup (python3.9)
4. Insert data into AWS Neptune
5. Wait for Step function to kick-off and see error in CloudWatch and/or Step Functions

Expected behavior
No error should happen. Data from Neptune should be indexed in OpenSearch

Plugins
N/A

Screenshots
If applicable, add screenshots to help explain your problem.

Host/Environment (please complete the following information):

• OS: N/A
• Version lambda puller python3.9 from s3://aws-neptune-customer-samples-eu-west-1/neptune-stream/lambda/python39/release_2022_07_27/neptune-to-es.zip
  
  

Additional context
version ElasticSearch 7.9 worked without issues. The problem appeared when we migrated to OpenSearch 2.5

[dblock]

I think this is because mapping type parameters were removed in 2.x, see https://opensearch.org/docs/2.0/breaking-changes/.

Are you following https://docs.aws.amazon.com/neptune/latest/userguide/full-text-search-cfn-create.html? I imagine we need to go fix it to support OpenSearch 2.x. I opened awslabs/amazon-neptune-tools#316.