fix: WPB-22439 - example of using proc_pull_ext_charts.sh

[mohitrajain]

This is a demo of how we can override builds.json values. I am trying to override a wire-utility version from current wire-builds to an older version.
wireapp/wire-builds@a5ca32d

proc_pull_ext_charts.sh - Pulls additional Helm charts from a custom JSON configuration file
This script complements proc_pull_charts.sh by fetching charts NOT included in the standard wire-builds
release (specified in extra_charts.json). It extracts chart metadata (name, repo, version) from the JSON,
then downloads each chart using helm pull with --untar to decompress them into ${OUTPUT_DIR}/charts.
If a chart already exists in the directory from the previous pull,we are removing them manually, to make space for
the specified version, ensuring the correct chart version is always available.

Changed from Ansible variable slicing (which failed with binary data) to file-based operations: The fix replaces direct byte extraction from decoded DER data using Ansible's b64decode and string slicing with shell commands that write DER data to files and use tail -c 32 to extract the exact 32-byte chunks needed for Ed25519 keys.

Change type

• Fix
• Feature
• Documentation
• Security / Upgrade

Basic information

• THIS CHANGE REQUIRES A DEPLOYMENT PACKAGE RELEASE
• THIS CHANGE REQUIRES A WIRE-DOCS RELEASE

Testing

• I ran/applied the changes myself, in a test environment.
• The CI job attached to this repo will test it for me.

Tracking

• I added a new entry in an appropriate subdirectory of changelog.d
• I mentioned this PR in Jira, OR I mentioned the Jira ticket in this PR.
• I mentioned this PR in one of the issues attached to one of our repositories.

Knowledge Transfer

• An Asciinema session is attached to the Jira ticket.

Motivation

Objective

Reason

Use case

[sonarqubecloud]

Quality Gate passed

Issues
3 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[mohitrajain]

closing it for #844