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

The test helpers lived in ordinary `testing.go` files inside the config, database, middleware and session packages, so they were built into the binary and the shared `test-support` lint rule could not see them. The four files are gone: the session's helpers move into its own `_test.go` file, and the rest into `configtest`, `databasetest` and `middlewaretest`, which the `depguard` deny list now names, so a non-test file importing them fails lint. The test-support packages build through the production constructors.

Judgement call: the session, the middleware and the webhook database manager now take the plain logger they log through, which the application wiring provides.
Judgement call: two idle-expiry tests move the stored timestamps back instead of advancing a fake clock.

Model: opus-5-5

cmd/webhooker/main.go

@@ -4,6 +4,7 @@ package main
 import (
 	"fmt"
 	"io"
+	"log/slog"
 	"os"
 	"time"
 
@@ -187,6 +188,9 @@ func newApp() *fx.App {
 		fx.Provide(
 			globals.New,
 			logger.New,
+			// The plain logger the session, the middleware and the
+			// webhook database manager take.
+			func(l *logger.Logger) *slog.Logger { return l.Get() },
 			config.New,
 			database.New,
 			database.NewWebhookDBManager,

cmd/webhooker/main_test.go

@@ -14,7 +14,7 @@ import (
 
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
-	"sneak.berlin/go/webhooker/internal/config"
+	"sneak.berlin/go/webhooker/internal/config/configtest"
 	"sneak.berlin/go/webhooker/internal/datadir"
 	"sneak.berlin/go/webhooker/internal/resetpw"
 	"sneak.berlin/go/webhooker/internal/server"
@@ -37,7 +37,7 @@ const dockerStopGrace = 10 * time.Second
 // fx.New applies options before it executes invokes, so the timeout
 // is set whether or not the graph itself can be constructed here.
 func TestNewApp_StopTimeout(t *testing.T) {
-	config.ClearEnvForTest(t)
+	configtest.ClearEnv(t)
 	t.Setenv("DATA_DIR", t.TempDir())
 
 	got := newApp().StopTimeout()
@@ -75,7 +75,7 @@ func freePort(t *testing.T) int {
 // anything is built, and the run of logger.New, which happens before
 // the configuration sets the level.
 func TestNewApp_SendsFxEventsToTheLogger(t *testing.T) {
-	config.ClearEnvForTest(t)
+	configtest.ClearEnv(t)
 	t.Setenv("DATA_DIR", t.TempDir())
 	t.Setenv("PORT", strconv.Itoa(freePort(t)))
 	t.Setenv("DEBUG", "true")