Take the signature, the expiry and the URL scheme off the image request (closes #314)

The image request now holds only its source and its transform, exactly what
the variant key covers. The /v1/image/ handler checks the allowlist and
verifies the signature itself with Signer.Verify(req, sig, expires). Both
image handlers keep the URL's expiry as a local value for Cache-Control. The
image service holds no signer, allowlist or AllowHTTP, and ValidateRequest is
gone. The fetcher takes the source and builds its URL with Source.URL from its
own AllowHTTP, so no URL string is built and parsed again. chooseAutoFormat
returns the format it chooses instead of writing into the request. The signed
URL format and every route's answers are unchanged.

Model: opus-5-5

internal/imgcache/testutil_internal_test.go

@@ -161,22 +161,11 @@ func generateTestGIF(t *testing.T, width, height int, c color.Color) []byte {
 }
 
 // SetupTestService creates a Service with mock fetcher for testing.
-func SetupTestService(
-	t *testing.T, opts ...TestServiceOption,
-) (*Service, *TestFixtures) {
+func SetupTestService(t *testing.T) (*Service, *TestFixtures) {
 	t.Helper()
 
 	mockFS, fixtures := NewTestFS(t)
 
-	cfg := &testServiceConfig{
-		allowlist:  []string{fixtures.GoodHost},
-		signingKey: "test-signing-key-must-be-32-chars",
-	}
-
-	for _, opt := range opts {
-		opt(cfg)
-	}
-
 	// Create temp directory for cache
 	tmpDir := t.TempDir()
 
@@ -199,8 +188,6 @@ func SetupTestService(
 			MaxInputBytes:           50 << 20,
 			MaxConcurrentProcessing: 2,
 		}),
-		SigningKey:      cfg.signingKey,
-		Allowlist:       cfg.allowlist,
 		MaxResponseSize: 50 << 20,
 	})
 	if err != nil {
@@ -228,32 +215,3 @@ func setupServiceTestDB(t *testing.T) *sql.DB {
 
 	return db
 }
-
-type testServiceConfig struct {
-	allowlist  []string
-	signingKey string
-}
-
-// TestServiceOption configures the test service.
-type TestServiceOption func(*testServiceConfig)
-
-// WithAllowlist sets the allowlist for the test service.
-func WithAllowlist(hosts ...string) TestServiceOption {
-	return func(c *testServiceConfig) {
-		c.allowlist = hosts
-	}
-}
-
-// WithSigningKey sets the signing key for the test service.
-func WithSigningKey(key string) TestServiceOption {
-	return func(c *testServiceConfig) {
-		c.signingKey = key
-	}
-}
-
-// WithNoAllowlist removes all allowlisted hosts.
-func WithNoAllowlist() TestServiceOption {
-	return func(c *testServiceConfig) {
-		c.allowlist = nil
-	}
-}