release.yaml does not handle absolute paths for manifestURI

[davidcassany]

The manifestURI does not handle absolute paths for file:// type. It should either error out with a meaningful message if they are not supported or actually enable loading an absolute path.

The path is always rebased on configuration directory path without checking if it is already an absolute path.

elemental/internal/config/config.go

Lines 167 to 172 in 660f73d

	absConfDir, err := filepath.Abs(configDir)
	if err != nil {
	return fmt.Errorf("calculate absolute directory: %w", err)
	}
	r.ManifestURI = filepath.Join(fileSource, absConfDir, strings.TrimPrefix(r.ManifestURI, fileSource))