Deprecate kubeconfig's preference field in favor of kuberc

Signed-off-by: Maciej Szulik <soltysh@gmail.com>

Kubernetes-commit: 8cf5e8db78deb186ef362f64ab779c09e9520156

tools/clientcmd/api/helpers_test.go

@@ -225,7 +225,6 @@ func Example_minifyAndShorten() {
 	//     cluster: cow-cluster
 	//     user: red-user
 	// current-context: federal-context
-	// preferences: {}
 	// users:
 	//   red-user:
 	//     client-certificate-data: DATA+OMITTED

tools/clientcmd/api/types.go

@@ -40,7 +40,8 @@ type Config struct {
 	// +optional
 	APIVersion string `json:"apiVersion,omitempty"`
 	// Preferences holds general information to be use for cli interactions
-	Preferences Preferences `json:"preferences"`
+	// Deprecated: this field is deprecated in v1.34. It is not used by any of the Kubernetes components.
+	Preferences Preferences `json:"preferences,omitzero"`
 	// Clusters is a map of referencable names to cluster configs
 	Clusters map[string]*Cluster `json:"clusters"`
 	// AuthInfos is a map of referencable names to user configs
@@ -55,6 +56,7 @@ type Config struct {
 }
 
 // IMPORTANT if you add fields to this struct, please update IsConfigEmpty()
+// Deprecated: this structure is deprecated in v1.34. It is not used by any of the Kubernetes components.
 type Preferences struct {
 	// +optional
 	Colors bool `json:"colors,omitempty"`
@@ -339,7 +341,6 @@ const (
 // NewConfig is a convenience function that returns a new Config object with non-nil maps
 func NewConfig() *Config {
 	return &Config{
-		Preferences: *NewPreferences(),
 		Clusters:   make(map[string]*Cluster),
 		AuthInfos:  make(map[string]*AuthInfo),
 		Contexts:   make(map[string]*Context),
@@ -370,6 +371,7 @@ func NewAuthInfo() *AuthInfo {
 
 // NewPreferences is a convenience function that returns a new
 // Preferences object with non-nil maps
+// Deprecated: this method is deprecated in v1.34. It is not used by any of the Kubernetes components.
 func NewPreferences() *Preferences {
 	return &Preferences{Extensions: make(map[string]runtime.Object)}
 }

tools/clientcmd/api/types_test.go

@@ -35,7 +35,6 @@ func Example_emptyConfig() {
 	// clusters: {}
 	// contexts: {}
 	// current-context: ""
-	// preferences: {}
 	// users: {}
 }
 

tools/clientcmd/api/v1/types.go

@@ -37,7 +37,8 @@ type Config struct {
 	// +optional
 	APIVersion string `json:"apiVersion,omitempty"`
 	// Preferences holds general information to be use for cli interactions
-	Preferences Preferences `json:"preferences"`
+	// Deprecated: this field is deprecated in v1.34. It is not used by any of the Kubernetes components.
+	Preferences Preferences `json:"preferences,omitzero"`
 	// Clusters is a map of referencable names to cluster configs
 	Clusters []NamedCluster `json:"clusters"`
 	// AuthInfos is a map of referencable names to user configs
@@ -51,6 +52,7 @@ type Config struct {
 	Extensions []NamedExtension `json:"extensions,omitempty"`
 }
 
+// Deprecated: this structure is deprecated in v1.34. It is not used by any of the Kubernetes components.
 type Preferences struct {
 	// +optional
 	Colors bool `json:"colors,omitempty"`

tools/clientcmd/loader_test.go

@@ -309,7 +309,6 @@ contexts:
   name: "433e40"
 current-context: any-context-value
 kind: Config
-preferences: {}
 users: null
 `)
 	if !bytes.Equal(expected, data) {
@@ -757,7 +756,6 @@ func Example_noMergingOnExplicitPaths() {
 	//   name: federal-context
 	// current-context: ""
 	// kind: Config
-	// preferences: {}
 	// users:
 	// - name: red-user
 	//   user:
@@ -809,7 +807,6 @@ func Example_mergingSomeWithConflict() {
 	//   name: federal-context
 	// current-context: federal-context
 	// kind: Config
-	// preferences: {}
 	// users:
 	// - name: red-user
 	//   user:
@@ -887,7 +884,6 @@ func Example_mergingEverythingNoConflicts() {
 	//   name: shaker-context
 	// current-context: ""
 	// kind: Config
-	// preferences: {}
 	// users:
 	// - name: black-user
 	//   user: