Support for opensearch serverless auth_type config

[assafcoh]

We would like support for aws opensearch serverless just like in the logstash-output-plugin

Our scenario requires migrating data from aws opensearch serverless to opensearch provisioned cluster.
Opensearch serverless does not support user/password access authorization. It supports access by iam users/roles.

When using latest logstach-input-opensearch plugin with config below we get error "auth_type" not recognized for opensearch"

input {
opensearch {
ecs_compatibility => disabled
index => "endpoint_discovery"
hosts => "https://123456.us-east-1.aoss.amazonaws.com:443"
auth_type => {
type => 'aws_iam'
aws_access_key_id => 'xxxxxxxxxxxxxxxxxx'
aws_secret_access_key => 'yyyyyyyyyyyyy'
region => 'us-east-1'
service_name => 'aoss'
}
legacy_template => false
default_server_major_version => 2
}
}

It would be great if auth_type config support will be added, just like for logstach-output-opensearch plugin

[JacobSiegle]

Duplicate - #24

[dblock]

Closing as dup.