feat: Support a list of values as string in the generators selectors

[damsien]

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Description

Closes #20943. Add a new valuesString field in the ApplicationSet object. A validation is done using the kubebuilder marker +kubebuilder:validation:XValidation:rule ensuring that either values or valuesString are specified but not both at the same time. The corresponding test have been added as well.

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Codecov Report

Attention: Patch coverage is 69.56522% with 14 lines in your changes missing coverage. Please review.

Please upload report for BASE (master@522d07a). Learn more about missing BASE report.

Files with missing lines	Patch %	Lines
applicationset/utils/selector.go	73.17%	9 Missing and 2 partials ⚠️
applicationset/generators/cluster.go	40.00%	2 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff            @@
##             master   #20972   +/-   ##
=========================================
  Coverage          ?   55.19%           
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  Files             ?      324           
  Lines             ?    55615           
  Branches          ?        0           
=========================================
  Hits              ?    30695           
  Misses            ?    22293           
  Partials          ?     2627           

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[damsien]

Hello @OpenGuidou, do you think that this implementation is okay?

[OpenGuidou]

Can you add new tests to cover the cluster generator and general post selector use cases ?

[damsien]

I created these 2 functions:

argo-cd/applicationset/utils/selector.go

Line 112 in 8fe2fda

func ApplicationMatchExpressionToMetaMatchExpression(me argov1alpha1.ApplicationMatchExpression) (*metav1.LabelSelectorRequirement, error) {

argo-cd/applicationset/utils/selector.go

Line 124 in 8fe2fda

func CustomSelectorToMetaSelector(selector argov1alpha1.LabelSelector) (*metav1.LabelSelector, error) {

in order to facilitate the conversion between the custom LabelSelector and the one from k8s metav1.LabelSelector.

One example of why it was necessary can be found in this function:

argo-cd/applicationset/generators/cluster.go

Lines 181 to 190 in 8fe2fda

	func (g *ClusterGenerator) getSecretsByClusterName(appSetGenerator *argoappsetv1alpha1.ApplicationSetGenerator) (map[string]corev1.Secret, error) {
	// List all Clusters:
	clusterSecretList := &corev1.SecretList{}
	metaSelector, err := utils.CustomSelectorToMetaSelector(appSetGenerator.Clusters.Selector)
	if err != nil {
	return nil, err
	}
	selector := metav1.AddLabelToSelector(metaSelector, common.LabelKeySecretType, common.LabelValueSecretTypeCluster)
	secretSelector, err := metav1.LabelSelectorAsSelector(selector)

It uses the metav1.AddLabelToSelector() function. If we don't add a conversion function, then it means that we have to rewrite the exact same AddLabelToSelector() function. I think that it is better to do the conversion as soon as possible in order to have less duplicate code from the metav1 package.

[OpenGuidou]

Great work, LGTM !