Fix platform engineering example and kubeconfig retriever

[anniegracehu]

Summary

Fixes the platform engineering (Custom MySQL) example and the consumer kubeconfig retrieval plugin so the example runs end-to-end.

Changes

plugins/kubeconfigretriever.py

• Use single quotes for the jsonpath argument so the shell does not alter it and kubectl returns the ConfigMap value (fixes empty output / "Expecting value: line 1 column 1").
• If the ConfigMap value is double-encoded JSON, parse it again so we get a dict (fixes TypeError: string indices must be integers, not 'str').
• Only read/update and print the kubeconfig when the parsed value is a dict, so we do not crash on bad or empty output.

Platform engineering example

• Bitnami images: Bitnami moved free images from docker.io/bitnami to docker.io/bitnamilegacy. The custom MySQL chart (and packaged tgz) now use bitnamilegacy/mysql, bitnamilegacy/os-shell, and bitnamilegacy/mysqld-exporter in charts/mysql/values.yaml so pods can pull images.
• steps.txt: Add a step to copy kubeplus-saas-provider.json into the example directory before step 4 so the following commands work without path prefixes.

Testing

• Ran through platform engineering steps (upload chart, create ResourceComposition, retrieve consumer kubeconfig, create CustomMysqlService instance).
• Confirmed MySQL pod runs and kubectl appresources, applogs, and metrics work.

[devdattakulkarni]

Nice!!
You mentioned above that unpackaged chart is also included. But I don't see it in the set of committed files.

[anniegracehu]

Nice!! You mentioned above that unpackaged chart is also included. But I don't see it in the set of committed files.

Yes, I realized it was too many files (around 60) so we will only have the packaged chart for now

[anniegracehu]

I have removed some comments in plugins/kubeconfigretriever.py

[devdattakulkarni]

Looks good!