Add PolylithMode base config option (#2428)

* Add `PolylithMode` base config option

* Polylith mode always uses HTTP APIs

cmd/dendrite-polylith-multi/main.go

@@ -71,7 +71,7 @@ func main() {
 
 	logrus.Infof("Starting %q component", component)
 
-	base := base.NewBaseDendrite(cfg, component) // TODO
+	base := base.NewBaseDendrite(cfg, component, base.PolylithMode) // TODO
 	defer base.Close()                                              // nolint: errcheck
 
 	go start(base, cfg)

setup/base/base.go

@@ -96,6 +96,7 @@ type BaseDendriteOptions int
 const (
 	NoCacheMetrics BaseDendriteOptions = iota
 	UseHTTPAPIs
+	PolylithMode
 )
 
 // NewBaseDendrite creates a new instance to be used by a component.
@@ -105,17 +106,20 @@ func NewBaseDendrite(cfg *config.Dendrite, componentName string, options ...Base
 	platformSanityChecks()
 	useHTTPAPIs := false
 	cacheMetrics := true
+	isMonolith := true
 	for _, opt := range options {
 		switch opt {
 		case NoCacheMetrics:
 			cacheMetrics = false
 		case UseHTTPAPIs:
 			useHTTPAPIs = true
+		case PolylithMode:
+			isMonolith = false
+			useHTTPAPIs = true
 		}
 	}
 
 	configErrors := &config.ConfigErrors{}
-	isMonolith := componentName == "Monolith" // TODO: better way?
 	cfg.Verify(configErrors, isMonolith)
 	if len(*configErrors) > 0 {
 		for _, err := range *configErrors {