Use dw dynamic config (#91882)

* Remove kubernetesPlaylists feature_toggle

* Remove unified_storage_mode

* Remove double import

* Read from config instead from feature_toggle

* cover scenario for when unified storage is not defined

* Be temporarily retro compatible with previous feature toggle

* Properly read unified_storage section

* [WIP] Read new format of config

* Fix test

* Fix other tests

* Generate feature flags file

* Use <group>.<resource> schema

* Use <group>.resource format on the FE as well

* Hide UniStore config from Frontend

Signed-off-by: Maicon Costa <maiconscosta@gmail.com>

* unwanted changes

* Use feature toggles in the FE. Enforce FTs are present before enabling dual writing
Co-authored-by: Ryan McKinley <ryantxu@users.noreply.github.com>

* use kubernetes playlists feature toggle on the FE

* Remove unwanted code

* Remove configs from the FE

* Remove commented code

* Add more explicit example

---------

Signed-off-by: Maicon Costa <maiconscosta@gmail.com>
Co-authored-by: Maicon Costa <maiconscosta@gmail.com>

pkg/setting/setting_unified_storage_test.go

@@ -0,0 +1,28 @@
+package setting
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestCfg_setUnifiedStorageConfig(t *testing.T) {
+	t.Run("read unified_storage configs", func(t *testing.T) {
+		cfg := NewCfg()
+		err := cfg.Load(CommandLineArgs{HomePath: "../../", Config: "../../conf/defaults.ini"})
+		assert.NoError(t, err)
+
+		s, err := cfg.Raw.NewSection("unified_storage.playlists.playlist.grafana.app")
+		assert.NoError(t, err)
+
+		_, err = s.NewKey("dualWriterMode", "2")
+		assert.NoError(t, err)
+
+		cfg.setUnifiedStorageConfig()
+
+		value, exists := cfg.UnifiedStorage["playlists.playlist.grafana.app"]
+
+		assert.Equal(t, exists, true)
+		assert.Equal(t, value, UnifiedStorageConfig{DualWriterMode: 2})
+	})
+}