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/httpfetcher/mock.go

@@ -7,14 +7,14 @@ import (
 	"io/fs"
 	"net/http"
 	"strings"
-)
 
-// errEmptyURLPath is returned when a mock URL has no usable path.
-var errEmptyURLPath = errors.New("empty URL path")
+	"sneak.berlin/go/pixa/internal/imagerequest"
+)
 
 // MockFetcher implements Fetcher using an embedded filesystem.
 // Files are organized as: hostname/path/to/file.ext
-// URLs like https://example.com/images/photo.jpg map to example.com/images/photo.jpg.
+// The source with host example.com and path /images/photo.jpg maps to
+// example.com/images/photo.jpg; the source query is ignored.
 type MockFetcher struct {
 	fs fs.FS
 }
@@ -24,8 +24,10 @@ func NewMock(fsys fs.FS) *MockFetcher {
 	return &MockFetcher{fs: fsys}
 }
 
-// Fetch retrieves content from the mock filesystem.
-func (m *MockFetcher) Fetch(ctx context.Context, url string) (*FetchResult, error) {
+// Fetch retrieves the source's content from the mock filesystem.
+func (m *MockFetcher) Fetch(
+	ctx context.Context, source imagerequest.Source,
+) (*FetchResult, error) {
 	// Check context cancellation
 	select {
 	case <-ctx.Done():
@@ -33,11 +35,7 @@ func (m *MockFetcher) Fetch(ctx context.Context, url string) (*FetchResult, erro
 	default:
 	}
 
-	// Parse URL to get filesystem path
-	path, err := urlToFSPath(url)
-	if err != nil {
-		return nil, err
-	}
+	path := source.Host + source.Path
 
 	// Open the file
 	f, err := m.fs.Open(path)
@@ -68,32 +66,6 @@ func (m *MockFetcher) Fetch(ctx context.Context, url string) (*FetchResult, erro
 	}, nil
 }
 
-// urlToFSPath converts a URL to a filesystem path.
-// https://example.com/images/photo.jpg -> example.com/images/photo.jpg
-func urlToFSPath(rawURL string) (string, error) {
-	// Strip scheme
-	url := rawURL
-	if idx := strings.Index(url, "://"); idx != -1 {
-		url = url[idx+3:]
-	}
-
-	// Remove query string
-	if idx := strings.Index(url, "?"); idx != -1 {
-		url = url[:idx]
-	}
-
-	// Remove fragment
-	if idx := strings.Index(url, "#"); idx != -1 {
-		url = url[:idx]
-	}
-
-	if url == "" {
-		return "", errEmptyURLPath
-	}
-
-	return url, nil
-}
-
 // detectContentTypeFromPath returns the MIME type based on file extension.
 func detectContentTypeFromPath(path string) string {
 	path = strings.ToLower(path)