MM-28859 Add feature flag managment system using split.io and remove viper. (#15954)

* Add feature flag managment system using split.io and remove viper.

* Fixing tests.

* Attempt to fix postgres tests.

* Fix watch filepath for advanced logging.

* Review fixes.

* Some error wrapping.

* Remove unessisary store interface.

* Desanitize SplitKey

* Simplify.

* Review feedback.

* Rename split mlog adatper to split logger.

* fsInner

* Style.

* Restore oldcfg test.

* Downgrading non-actionable feature flag errors to warnings.

Co-authored-by: Mattermod <mattermod@users.noreply.github.com>

app/server_test.go

@@ -65,7 +65,8 @@ func TestReadReplicaDisabledBasedOnLicense(t *testing.T) {
 
 	t.Run("Read Replicas with no License", func(t *testing.T) {
 		s, err := NewServer(func(server *Server) error {
-			configStore, _ := config.NewMemoryStoreWithOptions(&config.MemoryStoreOptions{InitialConfig: cfg.Clone()})
+			configStore := config.NewTestMemoryStore()
+			configStore.Set(&cfg)
 			server.configStore = configStore
 			return nil
 		})
@@ -77,8 +78,8 @@ func TestReadReplicaDisabledBasedOnLicense(t *testing.T) {
 
 	t.Run("Read Replicas With License", func(t *testing.T) {
 		s, err := NewServer(func(server *Server) error {
-			configStore, _ := config.NewMemoryStoreWithOptions(&config.MemoryStoreOptions{InitialConfig: cfg.Clone()})
-			server.configStore = configStore
+			configStore := config.NewTestMemoryStore()
+			configStore.Set(&cfg)
 			server.licenseValue.Store(model.NewTestLicense())
 			return nil
 		})
@@ -90,7 +91,8 @@ func TestReadReplicaDisabledBasedOnLicense(t *testing.T) {
 
 	t.Run("Search Replicas with no License", func(t *testing.T) {
 		s, err := NewServer(func(server *Server) error {
-			configStore, _ := config.NewMemoryStoreWithOptions(&config.MemoryStoreOptions{InitialConfig: cfg.Clone()})
+			configStore := config.NewTestMemoryStore()
+			configStore.Set(&cfg)
 			server.configStore = configStore
 			return nil
 		})
@@ -102,7 +104,8 @@ func TestReadReplicaDisabledBasedOnLicense(t *testing.T) {
 
 	t.Run("Search Replicas With License", func(t *testing.T) {
 		s, err := NewServer(func(server *Server) error {
-			configStore, _ := config.NewMemoryStoreWithOptions(&config.MemoryStoreOptions{InitialConfig: cfg.Clone()})
+			configStore := config.NewTestMemoryStore()
+			configStore.Set(&cfg)
 			server.configStore = configStore
 			server.licenseValue.Store(model.NewTestLicense())
 			return nil
@@ -114,27 +117,6 @@ func TestReadReplicaDisabledBasedOnLicense(t *testing.T) {
 	})
 }
 
-func TestStartServerRateLimiterCriticalError(t *testing.T) {
-	// Attempt to use Rate Limiter with an invalid config
-	ms, err := config.NewMemoryStoreWithOptions(&config.MemoryStoreOptions{
-		SkipValidation: true,
-	})
-	require.NoError(t, err)
-
-	config := ms.Get()
-	*config.RateLimitSettings.Enable = true
-	*config.RateLimitSettings.MaxBurst = -100
-	_, err = ms.Set(config)
-	require.NoError(t, err)
-
-	s, err := NewServer(ConfigStore(ms))
-	require.NoError(t, err)
-
-	serverErr := s.Start()
-	s.Shutdown()
-	require.Error(t, serverErr)
-}
-
 func TestStartServerPortUnavailable(t *testing.T) {
 	s, err := NewServer()
 	require.NoError(t, err)
@@ -398,7 +380,8 @@ func TestSentry(t *testing.T) {
 	testDir, _ := fileutils.FindDir("tests")
 	s, err := NewServer(func(server *Server) error {
 		configStore, _ := config.NewFileStore("config.json", true)
-		server.configStore = configStore
+		store, _ := config.NewStoreFromBacking(configStore)
+		server.configStore = store
 		server.UpdateConfig(func(cfg *model.Config) {
 			*cfg.ServiceSettings.ListenAddress = ":0"
 			*cfg.LogSettings.EnableSentry = false
@@ -441,7 +424,8 @@ func TestSentry(t *testing.T) {
 	SENTRY_DSN = fmt.Sprintf("http://test:test@localhost:%s/123", port)
 	s2, err := NewServer(func(server *Server) error {
 		configStore, _ := config.NewFileStore("config.json", true)
-		server.configStore = configStore
+		store, _ := config.NewStoreFromBacking(configStore)
+		server.configStore = store
 		server.UpdateConfig(func(cfg *model.Config) {
 			*cfg.ServiceSettings.ListenAddress = ":0"
 			*cfg.ServiceSettings.ConnectionSecurity = "TLS"