Removing _doc from data stream effective mappings

[masseyke]

This fixes the effective_mapping field of the get data stream API to match what is described in the specification. That is, there is no longer a _doc field at the top level of the mapping.

[elasticsearchmachine]

Pinging @elastic/es-data-management (Team:Data Management)

[Copilot]

Pull Request Overview

This PR removes the _doc field from the top level of data stream effective mappings to align with the API specification. The change ensures that the effective_mapping field in the get data stream API response no longer contains an unnecessary _doc wrapper around the actual mapping properties.

Key Changes

• Modified the getEffectiveMappings method to detect and unwrap _doc type placeholders from merged mappings
• Updated all test files to expect effective mappings without the _doc wrapper
• Removed unused DocumentMapper import

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
DataStream.java	Implements logic to detect and remove _doc wrapper from effective mappings
250_data_stream_mappings.yml	Updates YAML REST tests to expect mappings without _doc wrapper
TransportUpdateDataStreamMappingsActionIT.java	Updates integration tests to use mappings without _doc structure
DataStreamIT.java	Updates data stream integration tests to remove _doc from mapping definitions and expectations

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[dakrone]

LGTM assuming CI is happy

[elasticsearchmachine]

💔 Backport failed

Status	Branch	Result
❌	9.1	Commit could not be cherrypicked due to conflicts

You can use sqren/backport to manually backport by running backport --upstream elastic/elasticsearch --pr 134005