fix(lagoon/attach): store non-inline uploads with Content-Disposition attachment (quick-261028-rqe)

- attach.IsInlineContentType: the shared inline raster list (JPEG, PNG,
  GIF, WebP, AVIF), parameters and case ignored, false for empty or
  unparsable values
- writeBlob stores Content-Disposition: attachment for every other type,
  so a public bucket or CDN makes the browser download HTML, SVG, PDF or
  plain text; content_type and thumbnails are unchanged
- driver tests on memblob and fileblob, Postgres-backed Store assertion,
  lagoon README and the storage and attachments pages

modules/lagoon/attach/store.go

@@ -106,9 +106,13 @@ type Limits struct {
 // is then streamed into bucket at BlobKey of a server-generated disk name (22
 // random lowercase hex characters, a dot and the extension DiskExtension
 // derives from the sniffed type and the client extension, so a PNG named
-// x.html is stored as .png; file_name keeps the client's name); a body longer
-// than Limits.MaxBytes aborts the write, deletes the key and returns
-// ErrTooLarge. Finally it inserts the row with empty attachment columns,
+// x.html is stored as .png; file_name keeps the client's name). The blob's
+// Content-Type is the stored content type; a type IsInlineContentType does
+// not accept also gets Content-Disposition: attachment, so a public bucket or
+// CDN that sends the stored headers makes a browser download the file instead
+// of rendering it. The row's content_type holds the same type either way. A
+// body longer than Limits.MaxBytes aborts the write, deletes the key and
+// returns ErrTooLarge. Finally it inserts the row with empty attachment columns,
 // is_public from Upload.Public, the byte size and the content type, and sets
 // sort_order to the new id as WinterCMS's Sortable trait does. When the row
 // cannot be written the blob is deleted again.
@@ -201,7 +205,7 @@ func Store(ctx context.Context, db *gorm.DB, bucket *blob.Bucket, in Upload, lim
 func writeBlob(ctx context.Context, bucket *blob.Bucket, key string, r io.Reader, contentType string, limit int64) (int64, error) {
 	writeCtx, cancel := context.WithCancel(ctx)
 	defer cancel()
-	w, err := bucket.NewWriter(writeCtx, key, &blob.WriterOptions{ContentType: contentType})
+	w, err := bucket.NewWriter(writeCtx, key, uploadWriterOptions(contentType))
 	if err != nil {
 		return 0, fmt.Errorf("attach: blob writer: %w", err)
 	}