New session now expects a struct with everything it needs and a context (#228)

to pass along

provisioner/overlay.go

@@ -1,6 +1,7 @@
 package provisioner
 
 import (
+	"context"
 	"fmt"
 	"log"
 	"net/url"
@@ -20,7 +21,7 @@ func NewOverlaySessionProvisioner(df docker.FactoryApi) SessionProvisionerApi {
 	return &overlaySessionProvisioner{dockerFactory: df}
 }
 
-func (p *overlaySessionProvisioner) SessionNew(playground *types.Playground, s *types.Session) error {
+func (p *overlaySessionProvisioner) SessionNew(ctx context.Context, s *types.Session) error {
 	dockerClient, err := p.dockerFactory.GetForSession(s)
 	if err != nil {
 		// We assume we are out of capacity