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 CBOR field names, so tokens made before still decode. 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/golden_test.go

@@ -4,6 +4,7 @@ import (
 	"testing"
 	"time"
 
+	"sneak.berlin/go/pixa/internal/imagerequest"
 	"sneak.berlin/go/pixa/internal/signature"
 )
 
@@ -16,7 +17,7 @@ const goldenSigningKey = "golden-test-key"
 
 type goldenVector struct {
 	name string
-	req  signature.Request
+	req  imagerequest.Request
 	// wantSignature is the exact base64url (RFC 4648 URL-safe,
 	// padded) HMAC-SHA256 signature for the request with Expires
 	// set to goldenExpiresUnix.
@@ -34,15 +35,18 @@ func goldenVectors() []goldenVector {
 	return []goldenVector{
 		{
 			name: "resized without query",
-			req: signature.Request{
-				SourceHost:  testHost,
-				SourcePath:  testPath,
-				SourceQuery: "",
-				Width:       800,
-				Height:      600,
-				Format:      testFormatWebP,
-				Quality:     85,
-				FitMode:     testFitCover,
+			req: imagerequest.Request{
+				Source: imagerequest.Source{
+					Host:  testHost,
+					Path:  testPath,
+					Query: "",
+				},
+				Transform: imagerequest.Transform{
+					Size:    imagerequest.Size{Width: 800, Height: 600},
+					Format:  testFormatWebP,
+					Quality: 85,
+					FitMode: testFitCover,
+				},
 			},
 			// Signed data:
 			// "cdn.example.com:/photos/cat.jpg::800:600:webp:1704067200:85:cover"
@@ -51,15 +55,18 @@ func goldenVectors() []goldenVector {
 		},
 		{
 			name: "resized with query string",
-			req: signature.Request{
-				SourceHost:  testHost,
-				SourcePath:  testPath,
-				SourceQuery: "token=abc&v=2",
-				Width:       800,
-				Height:      600,
-				Format:      testFormatWebP,
-				Quality:     85,
-				FitMode:     testFitCover,
+			req: imagerequest.Request{
+				Source: imagerequest.Source{
+					Host:  testHost,
+					Path:  testPath,
+					Query: "token=abc&v=2",
+				},
+				Transform: imagerequest.Transform{
+					Size:    imagerequest.Size{Width: 800, Height: 600},
+					Format:  testFormatWebP,
+					Quality: 85,
+					FitMode: testFitCover,
+				},
 			},
 			// Signed data:
 			// "cdn.example.com:/photos/cat.jpg:token=abc&v=2:800:600:webp:1704067200:85:cover"
@@ -69,15 +76,18 @@ func goldenVectors() []goldenVector {
 		},
 		{
 			name: "original size without query",
-			req: signature.Request{
-				SourceHost:  testHost,
-				SourcePath:  testPath,
-				SourceQuery: "",
-				Width:       0,
-				Height:      0,
-				Format:      testFormatPNG,
-				Quality:     85,
-				FitMode:     testFitCover,
+			req: imagerequest.Request{
+				Source: imagerequest.Source{
+					Host:  testHost,
+					Path:  testPath,
+					Query: "",
+				},
+				Transform: imagerequest.Transform{
+					Size:    imagerequest.Size{Width: 0, Height: 0},
+					Format:  testFormatPNG,
+					Quality: 85,
+					FitMode: testFitCover,
+				},
 			},
 			// Signed data:
 			// "cdn.example.com:/photos/cat.jpg::0:0:png:1704067200:85:cover"
@@ -86,15 +96,18 @@ func goldenVectors() []goldenVector {
 		},
 		{
 			name: "non-default quality and fit",
-			req: signature.Request{
-				SourceHost:  testHost,
-				SourcePath:  testPath,
-				SourceQuery: "",
-				Width:       800,
-				Height:      600,
-				Format:      testFormatWebP,
-				Quality:     40,
-				FitMode:     testFitContain,
+			req: imagerequest.Request{
+				Source: imagerequest.Source{
+					Host:  testHost,
+					Path:  testPath,
+					Query: "",
+				},
+				Transform: imagerequest.Transform{
+					Size:    imagerequest.Size{Width: 800, Height: 600},
+					Format:  testFormatWebP,
+					Quality: 40,
+					FitMode: testFitContain,
+				},
 			},
 			// Signed data:
 			// "cdn.example.com:/photos/cat.jpg::800:600:webp:1704067200:40:contain"