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/imgcache/stats_internal_test.go

@@ -15,6 +15,7 @@ import (
 
 	"sneak.berlin/go/pixa/internal/database"
 	"sneak.berlin/go/pixa/internal/httpfetcher"
+	"sneak.berlin/go/pixa/internal/imagerequest"
 )
 
 func setupStatsTestDB(t *testing.T) *sql.DB {
@@ -319,13 +320,17 @@ func TestService_Get_CountsStats(t *testing.T) {
 	}
 
 	for _, step := range steps {
-		resp, err := svc.Get(t.Context(), &ImageRequest{
-			SourceHost: fixtures.GoodHost,
-			SourcePath: step.path,
-			Size:       Size{Width: step.size, Height: step.size},
-			Format:     FormatJPEG,
-			Quality:    85,
-			FitMode:    FitCover,
+		resp, err := svc.Get(t.Context(), &imagerequest.Request{
+			Source: imagerequest.Source{
+				Host: fixtures.GoodHost,
+				Path: step.path,
+			},
+			Transform: imagerequest.Transform{
+				Size:    imagerequest.Size{Width: step.size, Height: step.size},
+				Format:  imagerequest.FormatJPEG,
+				Quality: 85,
+				FitMode: imagerequest.FitCover,
+			},
 		})
 		if (err != nil) != step.wantErr {
 			t.Fatalf("%s: Get() error = %v, want error %t", step.name, err, step.wantErr)
@@ -419,13 +424,17 @@ func TestService_Get_CountsInterruptedMisses(t *testing.T) {
 
 			svc.fetcher = upstream
 
-			resp, err := svc.Get(ctx, &ImageRequest{
-				SourceHost: fixtures.GoodHost,
-				SourcePath: testPathPhoto,
-				Size:       Size{Width: 50, Height: 50},
-				Format:     FormatJPEG,
-				Quality:    85,
-				FitMode:    FitCover,
+			resp, err := svc.Get(ctx, &imagerequest.Request{
+				Source: imagerequest.Source{
+					Host: fixtures.GoodHost,
+					Path: testPathPhoto,
+				},
+				Transform: imagerequest.Transform{
+					Size:    imagerequest.Size{Width: 50, Height: 50},
+					Format:  imagerequest.FormatJPEG,
+					Quality: 85,
+					FitMode: imagerequest.FitCover,
+				},
 			})
 			t.Logf("Get() error = %v", err)
 
@@ -453,13 +462,17 @@ func TestService_Get_CountsHitAfterRequestEnds(t *testing.T) {
 
 	svc, fixtures := SetupTestService(t)
 
-	req := &ImageRequest{
-		SourceHost: fixtures.GoodHost,
-		SourcePath: testPathPhoto,
-		Size:       Size{Width: 50, Height: 50},
-		Format:     FormatJPEG,
-		Quality:    85,
-		FitMode:    FitCover,
+	req := &imagerequest.Request{
+		Source: imagerequest.Source{
+			Host: fixtures.GoodHost,
+			Path: testPathPhoto,
+		},
+		Transform: imagerequest.Transform{
+			Size:    imagerequest.Size{Width: 50, Height: 50},
+			Format:  imagerequest.FormatJPEG,
+			Quality: 85,
+			FitMode: imagerequest.FitCover,
+		},
 	}
 
 	// A first request caches the variant.