One image request type instead of five (closes #307)

The new package internal/imagerequest holds the request type, its two
parts Source and Transform, the Format and Fit types, the dimension and
fit checks, the /v1/image/ path parsing and the variant key; it imports
no other package of pixa. imgcache.ParsedURL, imgcache.ImageRequest,
signature.Request, imageprocessor.Request, the second Size, format and
fit types and the conversions between them are gone. The image
processor takes a Transform only. encurl keeps a private struct with the
token's short CBOR field names. VariantKey moves with the function that
makes it. Tests follow the moved and renamed code; the tests of the
removed conversions go with them.

Model: opus-5-5

internal/signature/escaping_test.go

@@ -5,6 +5,7 @@ import (
 	"testing"
 	"time"
 
+	"sneak.berlin/go/pixa/internal/imagerequest"
 	"sneak.berlin/go/pixa/internal/signature"
 )
 
@@ -16,32 +17,35 @@ func TestSigner_Verify_ColonCannotMovePathQueryBoundary(t *testing.T) {
 
 	signer := signature.New(goldenSigningKey)
 
-	signed := &signature.Request{
-		SourceHost: testHost,
-		SourcePath: "/a:b",
-		Width:      800,
-		Height:     600,
-		Format:     testFormatWebP,
-		Quality:    85,
-		FitMode:    testFitCover,
-		Expires:    time.Now().Add(1 * time.Hour),
+	signed := &imagerequest.Request{
+		Source: imagerequest.Source{
+			Host: testHost,
+			Path: "/a:b",
+		},
+		Transform: imagerequest.Transform{
+			Size:    imagerequest.Size{Width: 800, Height: 600},
+			Format:  testFormatWebP,
+			Quality: 85,
+			FitMode: testFitCover,
+		},
+		Expires: time.Now().Add(1 * time.Hour),
 	}
 	signed.Signature = signer.Sign(signed)
 
 	replayed := *signed
-	replayed.SourcePath = "/a"
-	replayed.SourceQuery = "b:"
+	replayed.Source.Path = "/a"
+	replayed.Source.Query = "b:"
 
 	t.Logf("signature for path %q query %q: %s",
-		signed.SourcePath, signed.SourceQuery, signed.Signature)
+		signed.Source.Path, signed.Source.Query, signed.Signature)
 	t.Logf("signature for path %q query %q: %s",
-		replayed.SourcePath, replayed.SourceQuery, signer.Sign(&replayed))
+		replayed.Source.Path, replayed.Source.Query, signer.Sign(&replayed))
 
 	err := signer.Verify(&replayed)
 	if !errors.Is(err, signature.ErrInvalid) {
 		t.Errorf("Verify() of path %q query %q with the signature for "+
 			"path %q = %v, want %v",
-			replayed.SourcePath, replayed.SourceQuery, signed.SourcePath,
+			replayed.Source.Path, replayed.Source.Query, signed.Source.Path,
 			err, signature.ErrInvalid)
 	}
 }
@@ -90,16 +94,19 @@ func TestSigner_EscapedGoldenVectors(t *testing.T) {
 		t.Run(tt.name, func(t *testing.T) {
 			t.Parallel()
 
-			req := &signature.Request{
-				SourceHost:  testHost,
-				SourcePath:  tt.path,
-				SourceQuery: tt.query,
-				Width:       800,
-				Height:      600,
-				Format:      testFormatWebP,
-				Quality:     85,
-				FitMode:     testFitCover,
-				Expires:     time.Unix(goldenExpiresUnix, 0),
+			req := &imagerequest.Request{
+				Source: imagerequest.Source{
+					Host:  testHost,
+					Path:  tt.path,
+					Query: tt.query,
+				},
+				Transform: imagerequest.Transform{
+					Size:    imagerequest.Size{Width: 800, Height: 600},
+					Format:  testFormatWebP,
+					Quality: 85,
+					FitMode: testFitCover,
+				},
+				Expires: time.Unix(goldenExpiresUnix, 0),
 			}
 
 			gotSignature := signer.Sign(req)