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

internal/actions/mocks/progress.go

@@ -0,0 +1,46 @@
+package mocks
+
+import (
+	"errors"
+	"github.com/containrrr/watchtower/pkg/session"
+	wt "github.com/containrrr/watchtower/pkg/types"
+)
+
+// CreateMockProgressReport creates a mock report from a given set of container states
+// All containers will be given a unique ID and name based on its state and index
+func CreateMockProgressReport(states ...session.State) wt.Report {
+
+	stateNums := make(map[session.State]int)
+	progress := session.Progress{}
+	failed := make(map[wt.ContainerID]error)
+
+	for _, state := range states {
+		index := stateNums[state]
+
+		switch state {
+		case session.SkippedState:
+			c, _ := CreateContainerForProgress(index, 41, "skip%d")
+			progress.AddSkipped(c, errors.New("unpossible"))
+			break
+		case session.FreshState:
+			c, _ := CreateContainerForProgress(index, 31, "frsh%d")
+			progress.AddScanned(c, c.ImageID())
+			break
+		case session.UpdatedState:
+			c, newImage := CreateContainerForProgress(index, 11, "updt%d")
+			progress.AddScanned(c, newImage)
+			progress.MarkForUpdate(c.ID())
+			break
+		case session.FailedState:
+			c, newImage := CreateContainerForProgress(index, 21, "fail%d")
+			progress.AddScanned(c, newImage)
+			failed[c.ID()] = errors.New("accidentally the whole container")
+		}
+
+		stateNums[state] = index + 1
+	}
+	progress.UpdateFailed(failed)
+
+	return progress.Report()
+
+}