refactor(surf): take the uploads inline types from attach.IsInlineContentType (quick-261028-rqe)

- the route's private inline list and its helper are gone; the
  disposition writer asks attach.IsInlineContentType, the same
  definition attach.Store uses for the disposition it stores
- headers are unchanged (TestUploadsResponseHeaders, TestUploadsMount)
- surf README and the storage page name the shared function

modules/surf/uploads.go

@@ -2,7 +2,6 @@ package surf
 
 import (
 	"fmt"
-	"mime"
 	"net/http"
 	"strings"
 
@@ -27,26 +26,20 @@ const defaultUploadsPrefix = "/storage/uploads"
 // embeds the file.
 const uploadsContentSecurityPolicy = "default-src 'none'; img-src 'self'; media-src 'self'; sandbox"
 
-// uploadsInlineTypes are the content types the uploads route lets a browser
-// show inline: raster images. Every other successful response, SVG and PDF
-// included, is served with Content-Disposition: attachment.
-var uploadsInlineTypes = map[string]bool{
-	"image/avif": true,
-	"image/gif":  true,
-	"image/jpeg": true,
-	"image/png":  true,
-	"image/webp": true,
-}
-
 // mountUploads registers GET {storage.uploads.public_path_prefix}/{path...}
 // when storage.uploads.serve is true. The handler delegates to
 // attach.StaticHandlerPublic, so missing rows and is_public=false rows 404.
 // Because the files are served on the app origin, every response carries
 // X-Content-Type-Options: nosniff and uploadsContentSecurityPolicy, and a
-// file whose stored type is not an inline raster image (uploadsInlineTypes)
-// is served as an attachment: attach.Store records the type sniffed from
-// the bytes, so an uploaded text file that starts with <html> is text/html. The bucket and the database are looked up per request:
-// boot and route:list build the router before serve publishes either.
+// file whose stored type is not an inline raster image
+// (attach.IsInlineContentType) is served as an attachment: attach.Store
+// records the type sniffed from the bytes, so an uploaded text file that
+// starts with <html> is text/html. attach.Store also stores the attachment
+// disposition with the blob, but the route still decides from the type on
+// every response: attach.StaticHandlerPublic sends only the stored type, and
+// blobs written earlier or outside attach.Store carry no disposition. The
+// bucket and the database are looked up per request: boot and route:list
+// build the router before serve publishes either.
 // The route owns the whole prefix: a plugin route at or under it fails
 // BuildRouter, as a route under the admin prefix does. With the key false
 // or absent nothing is registered and nothing is checked.
@@ -125,9 +118,9 @@ func uploadsHandler(app *backpack.App, pages *errorPages, prefix string) http.Ha
 
 // serveUploads runs next with the uploads response headers: nosniff and the
 // sandboxing CSP always, and Content-Disposition: attachment on a successful
-// response whose Content-Type is not in uploadsInlineTypes. The disposition
-// is decided when the status is written (or, for a HEAD that writes
-// nothing, when next returns), after next has set the Content-Type.
+// response whose Content-Type attach.IsInlineContentType rejects. The
+// disposition is decided when the status is written (or, for a HEAD that
+// writes nothing, when next returns), after next has set the Content-Type.
 func serveUploads(w http.ResponseWriter, req *http.Request, next http.Handler) {
 	w.Header().Set("X-Content-Type-Options", "nosniff")
 	w.Header().Set("Content-Security-Policy", uploadsContentSecurityPolicy)
@@ -148,7 +141,7 @@ func (w *uploadsDispositionWriter) decide(status int) {
 		return
 	}
 	w.decided = true
-	if status >= 200 && status < 300 && !uploadsInline(w.Header().Get("Content-Type")) {
+	if status >= 200 && status < 300 && !attach.IsInlineContentType(w.Header().Get("Content-Type")) {
 		w.Header().Set("Content-Disposition", "attachment")
 	}
 }
@@ -164,9 +157,3 @@ func (w *uploadsDispositionWriter) Write(p []byte) (int, error) {
 }
 
 func (w *uploadsDispositionWriter) Unwrap() http.ResponseWriter { return w.ResponseWriter }
-
-// uploadsInline reports whether contentType is an inline raster image.
-func uploadsInline(contentType string) bool {
-	mediaType, _, err := mime.ParseMediaType(contentType)
-	return err == nil && uploadsInlineTypes[strings.ToLower(mediaType)]
-}