docker: the container runtime as a module, with its tools in Go

Claims node-container-runtime (ADR 0207). Owns the packages, the socket and a weekly
prune of dangling images and unused build cache. Serves 18 tools over every container,
marking the mesh's. daemon.json, docker.service and the docker group are left to a
proposed change: dnsmasq and zsh declare them today, and the controller refuses a
second declaration (README).

modules/docker/cmd/docker-tools/tools_test.go

@@ -0,0 +1,60 @@
+package main
+
+import (
+	"encoding/json"
+	"os"
+	"reflect"
+	"sort"
+	"strings"
+	"testing"
+)
+
+func TestTheToolsServedAreTheToolsTheManifestNames(t *testing.T) {
+	raw, err := os.ReadFile("../../module.json")
+	if err != nil {
+		t.Fatal(err)
+	}
+	var m struct {
+		Tools []string `json:"tools"`
+	}
+	if err := json.Unmarshal(raw, &m); err != nil {
+		t.Fatal(err)
+	}
+	served := []string{}
+	for _, tool := range tools(client(&fake{}, 1000)) {
+		if !strings.HasPrefix(tool.Name, "docker_") || tool.Description == "" || tool.Run == nil {
+			t.Errorf("tool %q", tool.Name)
+		}
+		served = append(served, tool.Name)
+	}
+	sort.Strings(served)
+	listed := append([]string{}, m.Tools...)
+	sort.Strings(listed)
+	if !reflect.DeepEqual(served, listed) {
+		t.Fatalf("served %v, manifest %v", served, listed)
+	}
+}
+
+func TestNumbersAreDefaultedAndBounded(t *testing.T) {
+	if n, _ := bounded(map[string]any{}, "lines", 200, 2000); n != 200 {
+		t.Error(n)
+	}
+	if n, _ := bounded(map[string]any{"lines": float64(99999)}, "lines", 200, 2000); n != 2000 {
+		t.Error(n)
+	}
+	for _, bad := range []any{float64(0), float64(-1), float64(1.5), "10"} {
+		if _, err := bounded(map[string]any{"lines": bad}, "lines", 200, 2000); err == nil {
+			t.Errorf("%v accepted", bad)
+		}
+	}
+}
+
+func TestAStopFromTheToolNeedsAContainer(t *testing.T) {
+	for _, tool := range tools(client(&fake{}, 1000)) {
+		if tool.Name == "docker_stop" {
+			if _, err := tool.Run(map[string]any{}); err == nil {
+				t.Fatal("a stop without a container was accepted")
+			}
+		}
+	}
+}