api/types/events: define "Action" type and consts

Define consts for the Actions we use for events, instead of "ad-hoc" strings.
Having these consts makes it easier to find where specific events are triggered,
makes the events less error-prone, and allows documenting each Action (if needed).

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

daemon/pause.go

@@ -5,6 +5,7 @@ import (
 	"fmt"
 
 	"github.com/containerd/containerd/log"
+	"github.com/docker/docker/api/types/events"
 	"github.com/docker/docker/container"
 )
 
@@ -46,7 +47,7 @@ func (daemon *Daemon) containerPause(container *container.Container) error {
 	container.Paused = true
 	daemon.setStateCounter(container)
 	daemon.updateHealthMonitor(container)
-	daemon.LogContainerEvent(container, "pause")
+	daemon.LogContainerEvent(container, events.ActionPause)
 
 	if err := container.CheckpointTo(daemon.containersReplica); err != nil {
 		log.G(context.TODO()).WithError(err).Warn("could not save container to disk")