Add example environment configuration and Docker Compose setup

- Introduced a new `.env.example` file to provide a template for environment variables used by the Scratchbox server.
- Added a `docker-compose.example.yml` file to facilitate easy deployment of the Scratchbox service with Docker.
- Updated `docker-entrypoint.sh` to enforce environment variable settings for server configuration.
- Removed the generation of a config key file from the workflow, simplifying the configuration process.
- Adjusted the README.md to reflect changes in configuration management and usage instructions.

cmd/scratchbox/main_test.go

@@ -32,18 +32,6 @@ func repoRoot(t *testing.T) string {
 	return filepath.Clean(filepath.Join(filepath.Dir(file), "..", ".."))
 }
 
-func writeConfigKeyFile(t *testing.T, configPath string) {
-	t.Helper()
-	keyPath := filepath.Join(filepath.Dir(configPath), "config.key")
-	key, err := config.GenerateEncryptionKey()
-	if err != nil {
-		t.Fatalf("GenerateEncryptionKey() error = %v", err)
-	}
-	if err := os.WriteFile(keyPath, []byte(key+"\n"), 0o600); err != nil {
-		t.Fatalf("WriteFile(config.key) error = %v", err)
-	}
-}
-
 func TestMainProcessSuccess(t *testing.T) {
 	t.Parallel()
 
@@ -77,7 +65,6 @@ security:
 	if err := os.WriteFile(cfgPath, []byte(cfg), 0o644); err != nil {
 		t.Fatalf("WriteFile() error = %v", err)
 	}
-	writeConfigKeyFile(t, cfgPath)
 
 	cmd := exec.Command(os.Args[0], "-test.run=TestMainHelperProcess")
 	cmd.Dir = repoRoot(t)
@@ -105,6 +92,75 @@ func TestMainProcessBadConfigFails(t *testing.T) {
 	}
 }
 
+func TestMainProcessMissingConfigAutoGenerates(t *testing.T) {
+	t.Parallel()
+
+	tmp := t.TempDir()
+	cfgPath := filepath.Join(tmp, "nested", "config.yaml")
+
+	ctx, cancel := context.WithTimeout(context.Background(), 3*time.Second)
+	defer cancel()
+
+	cmd := exec.CommandContext(ctx, os.Args[0], "-test.run=TestMainHelperProcess")
+	cmd.Dir = repoRoot(t)
+	cmd.Env = append(os.Environ(),
+		"GO_WANT_MAIN_HELPER=1",
+		"MAIN_HELPER_MODE=missing-config-autogen",
+		"MAIN_HELPER_CONFIG="+cfgPath,
+	)
+	out, err := cmd.CombinedOutput()
+	if err != nil {
+		t.Fatalf("helper process failed: %v, output=%s", err, string(out))
+	}
+	if !strings.Contains(string(out), "Review and adjust it, then re-run the same command.") {
+		t.Fatalf("helper output missing expected guidance, output=%q", string(out))
+	}
+
+	raw, err := os.ReadFile(cfgPath)
+	if err != nil {
+		t.Fatalf("ReadFile(generated config) error = %v", err)
+	}
+	if !strings.Contains(string(raw), "server:") {
+		t.Fatalf("generated config missing expected section")
+	}
+}
+
+func TestMainProcessEnvSuccess(t *testing.T) {
+	t.Parallel()
+
+	tmp := t.TempDir()
+
+	cmd := exec.Command(os.Args[0], "-test.run=TestMainHelperProcess")
+	cmd.Dir = repoRoot(t)
+	cmd.Env = append(os.Environ(),
+		"GO_WANT_MAIN_HELPER=1",
+		"MAIN_HELPER_MODE=env-success",
+		"SCRATCHBOX_SERVER_LISTEN_ADDR=127.0.0.1:0",
+		"SCRATCHBOX_STORAGE_DATA_DIR="+filepath.Join(tmp, "data"),
+		"SCRATCHBOX_SECURITY_ALLOWED_IPS=",
+	)
+	if out, err := cmd.CombinedOutput(); err != nil {
+		t.Fatalf("helper process failed: %v, output=%s", err, string(out))
+	}
+}
+
+func TestServerConfigAndEnvMutuallyExclusive(t *testing.T) {
+	t.Parallel()
+
+	cmd := newRootCmd()
+	cmd.SetOut(io.Discard)
+	cmd.SetErr(io.Discard)
+	cmd.SetArgs([]string{"server", "--config", "config.yaml", "--env"})
+
+	err := cmd.Execute()
+	if err == nil {
+		t.Fatalf("expected error when both --config and --env are set")
+	}
+	if !strings.Contains(err.Error(), "none of the others can be") {
+		t.Fatalf("error = %q, want mutually exclusive flags error", err.Error())
+	}
+}
+
 func TestMainProcessStorageInitFails(t *testing.T) {
 	t.Parallel()
 
@@ -142,7 +198,6 @@ security:
 	if err := os.WriteFile(cfgPath, []byte(cfg), 0o644); err != nil {
 		t.Fatalf("WriteFile() error = %v", err)
 	}
-	writeConfigKeyFile(t, cfgPath)
 
 	cmd := exec.Command(os.Args[0], "-test.run=TestMainHelperProcess")
 	cmd.Dir = repoRoot(t)
@@ -181,6 +236,25 @@ func TestMainHelperProcess(t *testing.T) {
 		os.Args = []string{"scratchbox", "server", "--config", "/no/such/config.yaml"}
 		main()
 		os.Exit(0)
+	case "missing-config-autogen":
+		cfgPath := os.Getenv("MAIN_HELPER_CONFIG")
+		if cfgPath == "" {
+			os.Exit(2)
+		}
+		os.Args = []string{"scratchbox", "server", "--config", cfgPath}
+		main()
+		os.Exit(0)
+	case "env-success":
+		go func() {
+			time.Sleep(120 * time.Millisecond)
+			proc, err := os.FindProcess(os.Getpid())
+			if err == nil {
+				_ = proc.Signal(os.Interrupt)
+			}
+		}()
+		os.Args = []string{"scratchbox", "server", "--env"}
+		main()
+		os.Exit(0)
 	case "storage-fail":
 		cfgPath := os.Getenv("MAIN_HELPER_CONFIG")
 		os.Args = []string{"scratchbox", "server", "--config", cfgPath}
@@ -229,9 +303,6 @@ func TestGenerateConfigCommandWritesDefaultYAML(t *testing.T) {
 	if cfg.Storage.DataDir != "./data" {
 		t.Fatalf("storage.data_dir = %q, want %q", cfg.Storage.DataDir, "./data")
 	}
-	if cfg.Storage.EncryptionKeyFile != "config.key" {
-		t.Fatalf("storage.encryption_key_file = %q, want %q", cfg.Storage.EncryptionKeyFile, "config.key")
-	}
 	if cfg.Security.RateLimitUI.RequestsPerMinute != 360 {
 		t.Fatalf("security.rate_limit_ui.requests_per_minute = %d, want %d", cfg.Security.RateLimitUI.RequestsPerMinute, 360)
 	}
@@ -335,7 +406,6 @@ security:
 	if err := os.WriteFile(cfgPath, []byte(cfgRaw), 0o644); err != nil {
 		t.Fatalf("WriteFile() error = %v", err)
 	}
-	writeConfigKeyFile(t, cfgPath)
 
 	cfg, err := config.Load(cfgPath)
 	if err != nil {