Session report collection and report templates (#981)

* wip: notification stats

* make report notifications optional

* linting/documentation fixes

* linting/documentation fixes

* merge types.Container and container.Interface

* smaller naming/format fixes

* use typed image/container IDs

* simplify notifier and update tests

* add missed doc comments

* lint fixes

* remove unused constructors

* rename old/new current/latest

pkg/types/container.go

@@ -1,14 +1,53 @@
 package types
 
-import "github.com/docker/docker/api/types"
+import (
+	"github.com/docker/docker/api/types"
+	"strings"
+)
+
+// ImageID is a hash string representing a container image
+type ImageID string
+
+// ContainerID is a hash string representing a container instance
+type ContainerID string
+
+// ShortID returns the 12-character (hex) short version of an image ID hash, removing any "sha256:" prefix if present
+func (id ImageID) ShortID() (short string) {
+	return shortID(string(id))
+}
+
+// ShortID returns the 12-character (hex) short version of a container ID hash, removing any "sha256:" prefix if present
+func (id ContainerID) ShortID() (short string) {
+	return shortID(string(id))
+}
+
+func shortID(longID string) string {
+	prefixSep := strings.IndexRune(longID, ':')
+	offset := 0
+	length := 12
+	if prefixSep >= 0 {
+		if longID[0:prefixSep] == "sha256" {
+			offset = prefixSep + 1
+		} else {
+			length += prefixSep + 1
+		}
+	}
+
+	if len(longID) >= offset+length {
+		return longID[offset : offset+length]
+	}
+
+	return longID
+}
 
 // Container is a docker container running an image
 type Container interface {
 	ContainerInfo() *types.ContainerJSON
-	ID() string
+	ID() ContainerID
 	IsRunning() bool
 	Name() string
-	ImageID() string
+	ImageID() ImageID
+	SafeImageID() ImageID
 	ImageName() string
 	Enabled() (bool, bool)
 	IsMonitorOnly() bool