[elasticsearchexporter]: Add dynamic document id support for logs

[mauri870]

Description

This PR adds a new config option logs_dynamic_id that when set to true reads the elasticsearch.document_id attribute from each log record and uses it as the final document id in Elasticsearch. This is only implemented for logs but I can open subsequent PRs supporting metrics and traces akin to the *_dynamic_index options.

Fixes #36882

Testing

Added tests to verify that the document ID attribute can be read from the log record and that the _id is properly forwarded to Elasticsearch. Also asserted that when there is no doc id attribute the current behavior is retained.

Documentation

Updated the readme to mention the new logs_dynamic_id config option.

[carsonip]

looks good at a high level, thanks!

[carsonip]

Q: do you expect the elasticsearch.document_id to be indexed under attributes as well, or should it be ignored during serialization?

[mauri870]

Q: do you expect the elasticsearch.document_id to be indexed under attributes as well, or should it be ignored during serialization?

Haven't thought of that, but I think it makes sense to remove the field, as it only has meaning for the exporter.

Also, elasticsearch.document_id is overly specific, I'm happy to hear suggestions on the naming.

[mauri870]

I updated the code to remove the id field from the final document.

Regarding the attribute name, I wonder if we should stick to some kind of semantic convention such as https://opentelemetry.io/docs/specs/semconv/database/elasticsearch/. I scrolled throught it but couldn't find an existing attribute for a document id.

[carsonip]

Suggested change

	LogsDynamicID DynamicIndexSetting `mapstructure:"logs_dynamic_id"`
	LogsDynamicID bool `mapstructure:"logs_dynamic_id"`

nit: This has nothing to do with Index, which makes the use of DynamicIndexSetting slightly odd.

Also, personally I find this 1 level of nesting not very ergonomic. Unless we plan to add features to dynamic ID in the future e.g. logs_dynamic_id::attribute_name to make the attribute name configurable, I feel like adding a layer just to have a ::enabled bool not very useful. You can tell I'm already not very happy with *_dynamic_index::enabled. But I'd be interested to know other codeowners' opinion on this.