Keep test helpers out of the shipped binary (closes #506)

The four testing.go files in config, database, middleware and session
are gone. ClearEnvForTest moves to internal/config/configtest; the
webhook database manager helpers move to internal/database/databasetest
and the middleware's NewForTest to internal/middleware/middlewaretest,
both now built through the production constructors. Tests that wrapped
an open main database use database.Open. The session helpers move into
the session package's export_test.go; the middleware tests build their
session through session.New and age its timestamps instead of using a
fake clock.

The session, middleware and webhook database manager now take the
*slog.Logger they log through, so tests in other packages can give
them their own.

Model: opus-5-5

internal/delivery/queue_depth_gormlog_test.go

@@ -5,7 +5,6 @@ import (
 	"context"
 	"log/slog"
 	"net/http"
-	"path/filepath"
 	"strings"
 	"sync"
 	"testing"
@@ -14,11 +13,9 @@ import (
 	"github.com/google/uuid"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
-	"gorm.io/driver/sqlite"
-	"gorm.io/gorm"
 	"sneak.berlin/go/webhooker/internal/database"
+	"sneak.berlin/go/webhooker/internal/database/databasetest"
 	"sneak.berlin/go/webhooker/internal/delivery"
-	"sneak.berlin/go/webhooker/internal/gormlog"
 )
 
 // qdAggregateMarker identifies the queue-depth aggregate in the
@@ -49,27 +46,13 @@ func (q *qdSyncBuf) String() string {
 
 // qdMainDB opens a main database whose GORM logger is the service's
 // adapter, writing through log.
-func qdMainDB(t *testing.T, log *slog.Logger) *gorm.DB {
+func qdMainDB(t *testing.T, log *slog.Logger) *database.Database {
 	t.Helper()
 
-	sqlDB, err := database.OpenSQLite(
-		filepath.Join(t.TempDir(), "main-gormlog.db"),
-		database.SQLiteModeCreate,
-	)
+	db, err := database.Open(t.TempDir(), log)
 	require.NoError(t, err)
 
-	t.Cleanup(func() { _ = sqlDB.Close() })
-
-	db, err := gorm.Open(
-		sqlite.Dialector{Conn: sqlDB},
-		&gorm.Config{Logger: gormlog.New(log)},
-	)
-	require.NoError(t, err)
-
-	require.NoError(t, db.AutoMigrate(
-		&database.Webhook{},
-		&database.Target{},
-	))
+	t.Cleanup(func() { _ = db.Close() })
 
 	return db
 }
@@ -106,18 +89,18 @@ func TestQueueDepthSample_LogsNoBoundValue(t *testing.T) {
 	))
 
 	mainDB := qdMainDB(t, log)
-	dbMgr := database.NewTestWebhookDBManagerWithLogger(
-		t.TempDir(), log,
+	dbMgr := databasetest.NewTestWebhookDBManagerWithLogger(
+		t, t.TempDir(), log,
 	)
 
 	webhookID := uuid.New().String()
 	webhookDB := iSeedWebhookDB(t, dbMgr, webhookID)
 
-	iCreateWebhook(t, mainDB, webhookID, "queue-depth-gormlog")
+	iCreateWebhook(t, mainDB.DB(), webhookID, "queue-depth-gormlog")
 
 	targetID := uuid.New().String()
 
-	iCreateTarget(t, mainDB, targetID, webhookID,
+	iCreateTarget(t, mainDB.DB(), targetID, webhookID,
 		"queue-depth-gormlog-target", database.TargetTypeHTTP,
 		iHTTPConfig("https://example.com/hook"), 3,
 	)
@@ -136,7 +119,7 @@ func TestQueueDepthSample_LogsNoBoundValue(t *testing.T) {
 	)
 
 	engine := delivery.NewTestEngineWithDB(
-		database.NewTestDatabase(mainDB),
+		mainDB,
 		dbMgr,
 		log,
 		&http.Client{Timeout: 5 * time.Second},