fix(11-07): roll back the savepoint when a swallowed read failed

- beachcomber and lighthouse released their savepoint whenever the inner
  function reported no error; a Gate that counts a failed read as off,
  or a channel function or delete snapshot that swallows one, left the
  caller's Postgres transaction aborted (25P02) and failed the write
- a failed RELEASE now rolls back to the savepoint, as the READMEs promise
- beachcomber gets its testcontainers harness and sync tests
  (TestSyncGates, TestSyncAfterCommit, TestSyncDeleteAndSoftDelete,
  TestSyncFailuresNonFatal, TestServiceSetup); lighthouse gets
  TestBroadcastSwallowedReadFailure

modules/beachcomber/postgres_test.go

@@ -0,0 +1,148 @@
+package beachcomber
+
+import (
+	"context"
+	"database/sql"
+	"fmt"
+	"net/url"
+	"os"
+	"strings"
+	"sync/atomic"
+	"testing"
+	"time"
+
+	"git.golem15.com/golem15/summercms/modules/lagoon"
+	_ "github.com/jackc/pgx/v5/stdlib"
+	"github.com/testcontainers/testcontainers-go"
+	"github.com/testcontainers/testcontainers-go/modules/postgres"
+)
+
+var (
+	bcPG    *postgres.PostgresContainer
+	bcSQL   *sql.DB
+	bcDSN   string
+	bcPGErr error
+	dbSeq   atomic.Int64
+)
+
+func TestMain(m *testing.M) {
+	code := 1
+	if !testShort() {
+		ctx, cancel := context.WithTimeout(context.Background(), 2*time.Minute)
+		bcPGErr = startBeachcomberPostgres(ctx)
+		cancel()
+		if bcPGErr != nil {
+			fmt.Fprintf(os.Stderr, "beachcomber: testcontainers postgres: %v\n", bcPGErr)
+			stopBeachcomberPostgres()
+			os.Exit(1)
+		}
+	}
+	code = m.Run()
+	stopBeachcomberPostgres()
+	os.Exit(code)
+}
+
+func testShort() bool {
+	for _, a := range os.Args {
+		if a == "-test.short" {
+			return true
+		}
+	}
+	return false
+}
+
+func startBeachcomberPostgres(ctx context.Context) error {
+	ctr, err := postgres.Run(ctx,
+		"postgres:16-alpine",
+		postgres.WithDatabase("beachcomber"),
+		postgres.WithUsername("beachcomber"),
+		postgres.WithPassword("beachcomber"),
+		postgres.BasicWaitStrategies(),
+		testcontainers.WithEnv(map[string]string{
+			"POSTGRES_INITDB_ARGS": "--locale-provider=icu --icu-locale=pl-PL --encoding=UTF8",
+		}),
+	)
+	if err != nil {
+		return err
+	}
+	bcPG = ctr
+	dsn, err := ctr.ConnectionString(ctx, "sslmode=disable")
+	if err != nil {
+		return err
+	}
+	db, err := sql.Open("pgx", dsn)
+	if err != nil {
+		return err
+	}
+	if err := db.PingContext(ctx); err != nil {
+		_ = db.Close()
+		return err
+	}
+	bcSQL = db
+	bcDSN = dsn
+	return nil
+}
+
+func stopBeachcomberPostgres() {
+	if bcSQL != nil {
+		_ = bcSQL.Close()
+	}
+	if bcPG != nil {
+		_ = testcontainers.TerminateContainer(bcPG)
+	}
+}
+
+func adminDB(t *testing.T) *sql.DB {
+	t.Helper()
+	if testing.Short() {
+		t.Skip("requires testcontainers postgres")
+	}
+	if bcPGErr != nil {
+		t.Fatalf("postgres unavailable: %v", bcPGErr)
+	}
+	if bcSQL == nil {
+		t.Fatal("postgres unavailable: container was not started")
+	}
+	return bcSQL
+}
+
+// migratedDB returns a dedicated ICU pl-PL database migrated with
+// lagoon.Migrate (River v7 and summer_jobs) plus its DSN.
+func migratedDB(t *testing.T) (*sql.DB, string) {
+	t.Helper()
+	admin := adminDB(t)
+	ctx := t.Context()
+	name := fmt.Sprintf("beachcomber_%d", dbSeq.Add(1))
+	if _, err := admin.ExecContext(ctx, `CREATE DATABASE `+name+` TEMPLATE template0 ENCODING 'UTF8' LOCALE_PROVIDER icu ICU_LOCALE 'pl-PL'`); err != nil && !strings.Contains(err.Error(), "already exists") {
+		t.Fatalf("create %s: %v", name, err)
+	}
+	dsn, err := dsnWithDB(bcDSN, name)
+	if err != nil {
+		t.Fatal(err)
+	}
+	db, err := sql.Open("pgx", dsn)
+	if err != nil {
+		t.Fatal(err)
+	}
+	t.Cleanup(func() {
+		_ = db.Close()
+		_, _ = admin.ExecContext(context.Background(), `DROP DATABASE IF EXISTS `+name+` WITH (FORCE)`)
+	})
+	gdb, err := lagoon.Use(ctx, db)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := lagoon.Migrate(gdb, nil); err != nil {
+		t.Fatal(err)
+	}
+	return db, dsn
+}
+
+func dsnWithDB(dsn, name string) (string, error) {
+	u, err := url.Parse(dsn)
+	if err != nil {
+		return "", err
+	}
+	u.Path = "/" + name
+	return u.String(), nil
+}