Add support for PUT _ccr/follow

[jherns]

• Add support for following an index
• Update test framework to support CCR
  • will skip CCR tests if the replica isn't reachable
• Update readme

[Copilot]

PR Overview

This pull request adds support for following an index using the PUT _ccr/follow API and updates test infrastructure and documentation for CCR.

• Adds a new CCR client module with a follow method in the client library
• Introduces tests for following a leader index and sets up a replica client in the test helper
• Updates the README with CCR testing instructions

Changes

File	Description
test/client/ccr_test.rb	Adds tests to verify following a leader index using CCR
lib/elastomer_client/client/ccr.rb	Introduces the new CCR module and the follow method implementation
test/test_helper.rb	Configures the replica client for CCR tests
README.md	Updates usage instructions for CCR tests

Copilot reviewed 5 out of 5 changed files in this pull request and generated 1 comment.

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[Copilot]

The use of params.merge(params, ...) appears redundant and may lead to unexpected behavior. Consider simplifying it to params.merge(body: body, action: "follow", rest_api: "ccr") to avoid merging the same hash twice.

Suggested change

	response = client.put "/#{follower_index}/_ccr/follow", params.merge(params, body:, action: "follow", rest_api: "ccr")
	response = client.put "/#{follower_index}/_ccr/follow", params.merge(body: body, action: "follow", rest_api: "ccr")

[dtaivpp]

Should we at least check to make sure the following index was created here?

{ "follow_index_created" : true }

[jherns]

I think that is on the user (elastomer) to confirm the index was created.