Enable Grafana extensions at build time. (#11752)

* extensions: import and build

* bus: use predefined error

* enterprise: build script for enterprise packages

* poc: auto registering services and dependency injection

(cherry picked from commit b5b1ef875f905473af41e49f8071cb9028edc845)

* poc: backend services registry progress

(cherry picked from commit 97be69725881241bfbf1e7adf0e66801d6b0af3d)

* poc: minor update

(cherry picked from commit 03d7a6888b81403f458b94305792e075568f0794)

* ioc: introduce manuel ioc

* enterprise: adds setting for enterprise

* build: test and build specific ee commit

* cleanup: test testing code

* removes example hello service

pkg/bus/bus.go

@@ -2,7 +2,7 @@ package bus
 
 import (
 	"context"
-	"fmt"
+	"errors"
 	"reflect"
 )
 
@@ -10,6 +10,8 @@ type HandlerFunc interface{}
 type CtxHandlerFunc func()
 type Msg interface{}
 
+var ErrHandlerNotFound = errors.New("handler not found")
+
 type Bus interface {
 	Dispatch(msg Msg) error
 	DispatchCtx(ctx context.Context, msg Msg) error
@@ -38,12 +40,17 @@ func New() Bus {
 	return bus
 }
 
+// Want to get rid of global bus
+func GetBus() Bus {
+	return globalBus
+}
+
 func (b *InProcBus) DispatchCtx(ctx context.Context, msg Msg) error {
 	var msgName = reflect.TypeOf(msg).Elem().Name()
 
 	var handler = b.handlers[msgName]
 	if handler == nil {
-		return fmt.Errorf("handler not found for %s", msgName)
+		return ErrHandlerNotFound
 	}
 
 	var params = make([]reflect.Value, 2)
@@ -64,7 +71,7 @@ func (b *InProcBus) Dispatch(msg Msg) error {
 
 	var handler = b.handlers[msgName]
 	if handler == nil {
-		return fmt.Errorf("handler not found for %s", msgName)
+		return ErrHandlerNotFound
 	}
 
 	var params = make([]reflect.Value, 1)