Storage: Read desired mode from config instead of feature flags (#88353)

* Read desired mode from config
* Update playlist integration tests
* Add mode 1 playlist integration tests
* Add mode 0 dual writing to playlist integration tests
* Add documentation for the different dual writing modes

pkg/registry/apis/scope/register.go

@@ -17,6 +17,7 @@ import (
 
 	scope "github.com/grafana/grafana/pkg/apis/scope/v0alpha1"
 	"github.com/grafana/grafana/pkg/apiserver/builder"
+	grafanarest "github.com/grafana/grafana/pkg/apiserver/rest"
 	"github.com/grafana/grafana/pkg/services/featuremgmt"
 )
 
@@ -46,6 +47,11 @@ func (b *ScopeAPIBuilder) GetGroupVersion() schema.GroupVersion {
 	return scope.SchemeGroupVersion
 }
 
+func (b *ScopeAPIBuilder) GetDesiredDualWriterMode(dualWrite bool, modeMap map[string]grafanarest.DualWriterMode) grafanarest.DualWriterMode {
+	// Add required configuration support in order to enable other modes. For an example, see pkg/registry/apis/playlist/register.go
+	return grafanarest.Mode0
+}
+
 func (b *ScopeAPIBuilder) InstallSchema(scheme *runtime.Scheme) error {
 	err := scope.AddToScheme(scheme)
 	if err != nil {
@@ -114,7 +120,7 @@ func (b *ScopeAPIBuilder) GetAPIGroupInfo(
 	scheme *runtime.Scheme,
 	codecs serializer.CodecFactory,
 	optsGetter generic.RESTOptionsGetter,
-	_ bool, // dual write (not relevant)
+	_ grafanarest.DualWriterMode, // dual write desired mode (not relevant)
 ) (*genericapiserver.APIGroupInfo, error) {
 	apiGroupInfo := genericapiserver.NewDefaultAPIGroupInfo(scope.GROUP, scheme, metav1.ParameterCodec, codecs)