Alerting: Add integration test case for email channel (#36029)

Signed-off-by: Ganesh Vernekar <ganeshvern@gmail.com>

pkg/bus/bus.go

@@ -171,6 +171,11 @@ func (b *InProcBus) AddHandlerCtx(handler HandlerFunc) {
 	b.handlersWithCtx[queryTypeName] = handler
 }
 
+// GetHandlerCtx returns the handler function for the given struct name.
+func (b *InProcBus) GetHandlerCtx(name string) HandlerFunc {
+	return b.handlersWithCtx[name]
+}
+
 func (b *InProcBus) AddEventListener(handler HandlerFunc) {
 	handlerType := reflect.TypeOf(handler)
 	eventName := handlerType.In(0).Elem().Name()
@@ -211,6 +216,10 @@ func Publish(msg Msg) error {
 	return globalBus.Publish(msg)
 }
 
+func GetHandlerCtx(name string) HandlerFunc {
+	return globalBus.(*InProcBus).GetHandlerCtx(name)
+}
+
 func ClearBusHandlers() {
 	globalBus = New()
 }