Use enumer to generate String() methods for most enums

We have many hand-written String() methods (and similar) for enums.
These require more maintenance and are more error-prone than using
automatically generated methods. In addition, the auto-generated
versions can be more efficient.

Here, we switch to using https://github.com/loggerhead/enumer, itself
a fork of https://github.com/diegostamigni/enumer, no longer maintained,
and a fork of the mostly standard tool
https://pkg.go.dev/golang.org/x/tools/cmd/stringer.
We use this fork of enumer for Go 1.20+ compatibility and because
we require the `-transform` flag to be able to generate
constants that match our current code base.

Some enums were not targeted for this change:

* Bit sets, which are not supported by enumer or stringer.
* Enums with non-standard naming schemes, like having a common suffix
  instead of a prefix, or using spaces instead of underscores or dashes.
* Enums that don't have a type associated

api/lifetime_watcher.go

@@ -31,6 +31,7 @@ var (
 	DefaultRenewerRenewBuffer = 5
 )
 
+//go:generate enumer -type=RenewBehavior -trimprefix=RenewBehavior
 type RenewBehavior uint
 
 const (

api/plugin_runtime_types.go

@@ -9,11 +9,9 @@ package api
 
 import "fmt"
 
-var PluginRuntimeTypes = []PluginRuntimeType{
-	PluginRuntimeTypeUnsupported,
-	PluginRuntimeTypeContainer,
-}
+var PluginRuntimeTypes = _PluginRuntimeTypeValues
 
+//go:generate enumer -type=PluginRuntimeType -trimprefix=PluginRuntimeType -transform=snake
 type PluginRuntimeType uint32
 
 // This is a list of PluginRuntimeTypes used by Vault.
@@ -22,20 +20,11 @@ const (
 	PluginRuntimeTypeContainer
 )
 
-func (r PluginRuntimeType) String() string {
-	switch r {
-	case PluginRuntimeTypeContainer:
-		return "container"
-	default:
-		return "unsupported"
-	}
-}
-
+// ParsePluginRuntimeType is a wrapper around PluginRuntimeTypeString kept for backwards compatibility.
 func ParsePluginRuntimeType(PluginRuntimeType string) (PluginRuntimeType, error) {
-	switch PluginRuntimeType {
-	case "container":
-		return PluginRuntimeTypeContainer, nil
-	default:
+	t, err := PluginRuntimeTypeString(PluginRuntimeType)
+	if err != nil {
 		return PluginRuntimeTypeUnsupported, fmt.Errorf("%q is not a supported plugin runtime type", PluginRuntimeType)
 	}
+	return t, nil
 }

builtin/logical/pki/path_config_acme.go

@@ -394,6 +394,7 @@ func getDefaultDirectoryPolicyType(defaultDirectoryPolicy string) (DefaultDirect
 	}
 }
 
+//go:generate enumer -type=DefaultDirectoryPolicyType
 type DefaultDirectoryPolicyType int
 
 const (

builtin/logical/pki/path_tidy.go

@@ -23,15 +23,16 @@ import (
 
 var tidyCancelledError = errors.New("tidy operation cancelled")
 
+//go:generate enumer -type=tidyStatusState -trimprefix=tidyStatus
 type tidyStatusState int
 
 const (
-	tidyStatusInactive   tidyStatusState = iota
-	tidyStatusStarted                    = iota
-	tidyStatusFinished                   = iota
-	tidyStatusError                      = iota
-	tidyStatusCancelling                 = iota
-	tidyStatusCancelled                  = iota
+	tidyStatusInactive tidyStatusState = iota
+	tidyStatusStarted
+	tidyStatusFinished
+	tidyStatusError
+	tidyStatusCancelling
+	tidyStatusCancelled
 )
 
 type tidyStatus struct {

builtin/logical/pki/util.go

@@ -253,15 +253,16 @@ func parseIfNotModifiedSince(req *logical.Request) (time.Time, error) {
 	return headerTimeValue, nil
 }
 
+//go:generate enumer -type=ifModifiedReqType -trimprefix=ifModified
 type ifModifiedReqType int
 
 const (
-	ifModifiedUnknown         ifModifiedReqType = iota
-	ifModifiedCA                                = iota
-	ifModifiedCRL                               = iota
-	ifModifiedDeltaCRL                          = iota
-	ifModifiedUnifiedCRL                        = iota
-	ifModifiedUnifiedDeltaCRL                   = iota
+	ifModifiedUnknown ifModifiedReqType = iota
+	ifModifiedCA
+	ifModifiedCRL
+	ifModifiedDeltaCRL
+	ifModifiedUnifiedCRL
+	ifModifiedUnifiedDeltaCRL
 )
 
 type IfModifiedSinceHelper struct {