add get all action for sampling configs

[seanzatzdev]

adds the get endpoint for all sampling configs; e.g.

GET /_sample/config

returns:

[
  {
    "index": "logs",
    "configuration:
    {
      "rate": "5%",
      "if": "ctx?.network?.name == 'Guest'"
    }
  },
  {
    "index": "my-index",
    "configuration:
    {
      "rate": "25%"
    }
  }
]

[Copilot]

Pull Request Overview

This PR adds a new GET endpoint /_sample/config to retrieve all sampling configurations across the cluster. The endpoint returns an array of objects containing index names and their associated sampling configurations.

Key changes:

• Introduced GetAllSampleConfigurationAction with request/response classes supporting cluster-wide configuration retrieval
• Added transport and REST handlers for the new action
• Implemented comprehensive test coverage including unit, integration, and YAML REST tests

Reviewed Changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
GetAllSampleConfigurationAction.java	Defines the action type, request/response classes with serialization and XContent support
TransportGetAllSampleConfigurationAction.java	Implements transport layer logic to retrieve all sampling configurations from cluster metadata
RestGetAllSampleConfigurationAction.java	REST handler mapping GET /_sample/config to the transport action
ActionModule.java	Registers the new action and REST handler
Constants.java	Adds the new action privilege string
GetAllSampleConfigurationActionRequestTests.java	Unit tests for request serialization and task creation
GetAllSampleConfigurationActionResponseTests.java	Unit tests for response serialization with mutation testing
GetAllSampleConfigurationActionIT.java	Integration tests covering various scenarios
10_basic.yml	YAML REST API tests
indices.get_all_sample_configuration.json	REST API specification

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[elasticsearchmachine]

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

[seanzatzdev]

Looks like the yaml rest tests are all getting "connection refused" for some reason, not sure what that's about but seems like it must be a wider problem since all of the yaml tests i didnt touch are getting it

[masseyke]

Looks good to me, with the exception of the unreachable test code I commented on.