MM-21357: Use typed constants ClusterEvent (#17920)

* MM-21357: Use typed constants ClusterEvent

Use typed constants for:
- model.ClusterEvent

https://mattermost.atlassian.net/browse/MM-21357

```release-note
Use typed constant for model.ClusterEvent
```

* trigger CI
```release-note
NONE
```

services/cache/cache.go

@@ -6,6 +6,8 @@ package cache
 import (
 	"errors"
 	"time"
+
+	"github.com/mattermost/mattermost-server/v5/model"
 )
 
 // ErrKeyNotFound is the error when the given key is not found
@@ -42,7 +44,7 @@ type Cache interface {
 	Len() (int, error)
 
 	// GetInvalidateClusterEvent returns the cluster event configured when this cache was created.
-	GetInvalidateClusterEvent() string
+	GetInvalidateClusterEvent() model.ClusterEvent
 
 	// Name returns the name of the cache
 	Name() string

services/cache/lru.go

@@ -24,7 +24,7 @@ type LRU struct {
 	items                  map[string]*list.Element
 	defaultExpiry          time.Duration
 	name                   string
-	invalidateClusterEvent string
+	invalidateClusterEvent model.ClusterEvent
 }
 
 // LRUOptions contains options for initializing LRU cache
@@ -32,7 +32,7 @@ type LRUOptions struct {
 	Name                   string
 	Size                   int
 	DefaultExpiry          time.Duration
-	InvalidateClusterEvent string
+	InvalidateClusterEvent model.ClusterEvent
 	// StripedBuckets is used only by LRUStriped and shouldn't be greater than the number
 	// of CPUs available on the machine running this cache.
 	StripedBuckets int
@@ -128,7 +128,7 @@ func (l *LRU) Len() (int, error) {
 }
 
 // GetInvalidateClusterEvent returns the cluster event configured when this cache was created.
-func (l *LRU) GetInvalidateClusterEvent() string {
+func (l *LRU) GetInvalidateClusterEvent() model.ClusterEvent {
 	return l.invalidateClusterEvent
 }
 

services/cache/lru_striped.go

@@ -9,6 +9,8 @@ import (
 	"time"
 
 	"github.com/cespare/xxhash/v2"
+
+	"github.com/mattermost/mattermost-server/v5/model"
 )
 
 // LRUStriped keeps LRU caches in buckets in order to lower mutex contention.
@@ -39,7 +41,7 @@ import (
 type LRUStriped struct {
 	buckets                []*LRU
 	name                   string
-	invalidateClusterEvent string
+	invalidateClusterEvent model.ClusterEvent
 }
 
 func (L LRUStriped) hashkeyMapHash(key string) uint64 {
@@ -108,7 +110,7 @@ func (L LRUStriped) Len() (int, error) {
 }
 
 // GetInvalidateClusterEvent does the same as LRU.GetInvalidateClusterEvent
-func (L LRUStriped) GetInvalidateClusterEvent() string {
+func (L LRUStriped) GetInvalidateClusterEvent() model.ClusterEvent {
 	return L.invalidateClusterEvent
 }
 

services/cache/provider.go

@@ -5,6 +5,8 @@ package cache
 
 import (
 	"time"
+
+	"github.com/mattermost/mattermost-server/v5/model"
 )
 
 // CacheOptions contains options for initializaing a cache
@@ -12,7 +14,7 @@ type CacheOptions struct {
 	Size                   int
 	DefaultExpiry          time.Duration
 	Name                   string
-	InvalidateClusterEvent string
+	InvalidateClusterEvent model.ClusterEvent
 	Striped                bool
 	StripedBuckets         int
 }

services/cache/provider_test.go

@@ -7,6 +7,7 @@ import (
 	"testing"
 	"time"
 
+	"github.com/mattermost/mattermost-server/v5/model"
 	"github.com/stretchr/testify/require"
 )
 
@@ -56,7 +57,7 @@ func TestNewCache(t *testing.T) {
 
 		size := 1
 		expiry := 1 * time.Second
-		event := "clusterEvent"
+		event := model.ClusterEvent("clusterEvent")
 		c, err := p.NewCache(&CacheOptions{
 			Size:                   size,
 			Name:                   "name",
@@ -139,7 +140,7 @@ func TestNewCache_Striped(t *testing.T) {
 
 		size := 1
 		expiry := 1 * time.Second
-		event := "clusterEvent"
+		event := model.ClusterEvent("clusterEvent")
 		c, err := p.NewCache(&CacheOptions{
 			Size:                   size,
 			Name:                   "name",