Update helm chart Readme with custom plugin config

[rahulgurnani]

What type of PR is this?

/kind bug

What this PR does / why we need it:

Fixes helm chart to support reading EPP plugin config from a yaml file

Which issue(s) this PR fixes:

Fixes #1465

Does this PR introduce a user-facing change?:

Add support to pass custom plugin config to EPP

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[k8s-ci-robot]

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[nirrozenbaum]

@rahulgurnani can you explain the idea of this PR?
current helm chart in main supports plugin config from yaml through the helm chart (due to a bug that wasn't possible but bug was fixed in #1508).
we should cherry pick that fix and publish RC3 soon.
after that fix customPluginsConfig should be set through the helm chart as the example shows in the values.yaml file:

gateway-api-inference-extension/config/charts/inferencepool/values.yaml

Lines 16 to 28 in a634467

	# This is the plugins configuration file.
	# pluginsCustomConfig:
	# custom-plugins.yaml: |
	# apiVersion: inference.networking.x-k8s.io/v1alpha1
	# kind: EndpointPickerConfig
	# plugins:
	# - type: custom-scorer
	# parameters:
	# custom-threshold: 64
	# schedulingProfiles:
	# - name: default
	# plugins:
	# - pluginRef: custom-scorer

[rahulgurnani]

@rahulgurnani can you explain the idea of this PR? current helm chart in main supports plugin config from yaml through the helm chart (due to a bug that wasn't possible but bug was fixed in #1508). we should cherry pick that fix and publish RC3 soon. after that fix customPluginsConfig should be set through the helm chart as the example shows in the values.yaml file:

gateway-api-inference-extension/config/charts/inferencepool/values.yaml

Lines 16 to 28 in a634467

	# This is the plugins configuration file.
	# pluginsCustomConfig:
	# custom-plugins.yaml: |
	# apiVersion: inference.networking.x-k8s.io/v1alpha1
	# kind: EndpointPickerConfig
	# plugins:
	# - type: custom-scorer
	# parameters:
	# custom-threshold: 64
	# schedulingProfiles:
	# - name: default
	# plugins:
	# - pluginRef: custom-scorer

We presently don't mention about the customPluginsConfig in the README file:
https://github.com/kubernetes-sigs/gateway-api-inference-extension/blob/main/config/charts/inferencepool/README.md

So from a user of helm chart perspective, I was thinking, if we can pass it from a local file yaml file and update readme accordingly, it may be more suitable. So you write custom plugin config in a yaml and pass the path to the config file as a parameter to the helm chart. So we can move this change in the values.yaml.

After looking at your change, I think we can do that as well. We just need to modify the Readme as well.

[nirrozenbaum]

We presently don't mention about the customPluginsConfig in the README file:
https://github.com/kubernetes-sigs/gateway-api-inference-extension/blob/main/config/charts/inferencepool/README.md

you're correct. good catch!
This should definitely be covered in the README.md. I think it should be added in the table at the bottom but it's a central piece of the configuration so it's worth adding a dedicated section about it. so like we have Install with Custom Environment Variables section, we should have Install with Custom Plugins Configuration section.

[rahulgurnani]

@nirrozenbaum
Sounds good, updated the readme in this PR.

[kfswain]

/ok-to-test
/approve

[nirrozenbaum]

/lgtm
/approve

Thanks @rahulgurnani!

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: kfswain, nirrozenbaum, rahulgurnani

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