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/handlers/format_auto.go

@@ -8,7 +8,7 @@ import (
 	"strconv"
 	"strings"
 
-	"sneak.berlin/go/pixa/internal/imgcache"
+	"sneak.berlin/go/pixa/internal/imagerequest"
 )
 
 // Errors for an Accept header that an auto URL cannot be served for.
@@ -24,9 +24,9 @@ var (
 // header that is not valid and 406 for one that allows none of the formats,
 // and reports whether req can be served. Any other format is left as it is.
 func (s *Handlers) chooseAutoFormat(
-	w http.ResponseWriter, r *http.Request, req *imgcache.ImageRequest,
+	w http.ResponseWriter, r *http.Request, req *imagerequest.Request,
 ) bool {
-	if req.Format != imgcache.FormatAuto {
+	if req.Transform.Format != imagerequest.FormatAuto {
 		return true
 	}
 
@@ -45,7 +45,7 @@ func (s *Handlers) chooseAutoFormat(
 		return false
 	}
 
-	req.Format = format
+	req.Transform.Format = format
 
 	return true
 }
@@ -56,26 +56,26 @@ func (s *Handlers) chooseAutoFormat(
 // specific entry of image/jpeg, image/* and */* allows it, or when it names
 // nothing. A q of 0 refuses a format. JPEG XL, AVIF and WebP must be named, as
 // clients that cannot show them send image/* and */* too.
-func formatForAccept(accept string) (imgcache.ImageFormat, error) {
+func formatForAccept(accept string) (imagerequest.Format, error) {
 	qualities, err := parseAccept(accept)
 	if err != nil {
 		return "", err
 	}
 
 	if len(qualities) == 0 {
-		return imgcache.FormatJPEG, nil
+		return imagerequest.FormatJPEG, nil
 	}
 
 	if qualities["image/jxl"] > 0 {
-		return imgcache.FormatJXL, nil
+		return imagerequest.FormatJXL, nil
 	}
 
 	if qualities["image/avif"] > 0 {
-		return imgcache.FormatAVIF, nil
+		return imagerequest.FormatAVIF, nil
 	}
 
 	if qualities["image/webp"] > 0 {
-		return imgcache.FormatWebP, nil
+		return imagerequest.FormatWebP, nil
 	}
 
 	// For JPEG, the most specific entry the header has decides
@@ -89,7 +89,7 @@ func formatForAccept(accept string) (imgcache.ImageFormat, error) {
 	}
 
 	if quality > 0 {
-		return imgcache.FormatJPEG, nil
+		return imagerequest.FormatJPEG, nil
 	}
 
 	return "", errNotAcceptable