Backport PR #17039 to 8.18: Fix logstash-keystore to accept spaces in values when added via stdin

[github-actions]

Backport PR #17039 to 8.18 branch, original message:

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Release notes

Fix logstash-keystore to accept spaces in values when added via stdin

What does this PR do?

logstash-keystore incorrectly handled values containing spaces, causing only the first word to be stored.
For example, a value like "Hello, world!" was split, resulting in "Hello," as the stored value instead of the full string.
This commit preserves spaces in values, ensuring that multi-word strings are stored as intended.

Why is it important/What is the impact to the user?

This issue mainly affected ECK users who followed best practices for managing secure settings, leading to incorrect value assignments.

apiVersion: v1
kind: Secret
metadata:
  name: logstash-secure-settings
  namespace: logstash-sample
stringData:
  hello: "Hello, world!"
  bye: "bye"

Users who use stdin to add value are impacted as well. For example, echo "somevalue" | bin/logstash-keystore add hello

Checklist

• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have made corresponding change to the default configuration files (and/or docker env variables)
• I have added tests that prove my fix is effective or that my feature works

Author's Checklist

• [ ]

How to test this PR locally

echo "hello world" | bin/logstash-keystore add hello
bin/logstash -e "input{ generator{ count => 1 tags => ['${hello}'] }}"

it should print "hello world"

Related issues

• closes: Logstash keystore --stdin option #11436

Use cases

Screenshots

Logs

[kaisecheng]

LGTM

[elastic-sonarqube]

Quality Gate passed

Issues
0 New issues
0 Fixed issues
0 Accepted issues

Measures
0 Security Hotspots
No data about Coverage
No data about Duplication

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[elasticmachine]

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