Add template for deprecation feature

Author: HirazawaUi

api/approval.go

@@ -41,7 +41,8 @@ type PRRApproval struct {
 	Beta       *PRRMilestone `json:"beta" yaml:"beta,omitempty"`
 	Stable     *PRRMilestone `json:"stable" yaml:"stable,omitempty"`
 	Deprecated *PRRMilestone `json:"deprecated" yaml:"deprecated,omitempty"`
-	Removed    *PRRMilestone `json:"removed", yaml:"removed,omitempty"`
+	Removed    *PRRMilestone `json:"removed" yaml:"removed,omitempty"`
+	Disabled   *PRRMilestone `json:"disabled" yaml:"disabled,omitempty"`
 
 	// TODO(api): Move to separate struct for handling document parsing
 	Error error `json:"-" yaml:"-"`

api/proposal.go

@@ -36,12 +36,18 @@ const (
 	AlphaStage  Stage = "alpha"
 	BetaStage   Stage = "beta"
 	StableStage Stage = "stable"
+	Deprecated  Stage = "deprecated"
+	Disabled    Stage = "disabled"
+	Removed     Stage = "removed"
 )
 
 var ValidStages = []Stage{
 	AlphaStage,
 	BetaStage,
 	StableStage,
+	Deprecated,
+	Disabled,
+	Removed,
 }
 
 func (s Stage) IsValid() error {
@@ -138,6 +144,7 @@ type Milestone struct {
 	Stable     string `json:"stable" yaml:"stable"`
 	Deprecated string `json:"deprecated" yaml:"deprecated,omitempty"`
 	Removed    string `json:"removed" yaml:"removed,omitempty"`
+	Disabled   string `json:"disabled" yaml:"disabled,omitempty"`
 }
 
 type FeatureGate struct {

keps/NNNN-kep-template/kep.yaml

@@ -22,6 +22,8 @@ replaces:
   - "/keps/sig-ccc/3456-replaced-kep"
 
 # The target maturity stage in the current dev cycle for this KEP.
+# If the purpose of this KEP is to deprecate a user-visible feature
+# and a Deprecated feature gates are added, they should be deprecated|disabled|removed.
 stage: alpha|beta|stable
 
 # The most recent milestone for which work toward delivery of this KEP has been