Simplify resources code, enabling any resource to be overridden (not just translations)

resources/embed.go

@@ -3,10 +3,19 @@ package resources
 import (
 	"embed"
 	"io"
+	"io/fs"
+	"os"
+	"path"
+
+	"github.com/navidrome/navidrome/conf"
+	"github.com/navidrome/navidrome/utils"
 )
 
-//go:embed *
-var FS embed.FS
+var (
+	//go:embed *
+	fsys embed.FS
+	FS   fs.FS
+)
 
 func Asset(path string) ([]byte, error) {
 	f, err := FS.Open(path)
@@ -15,3 +24,10 @@ func Asset(path string) ([]byte, error) {
 	}
 	return io.ReadAll(f)
 }
+
+func init() {
+	FS = utils.MergeFS{
+		Base:    fsys,
+		Overlay: os.DirFS(path.Join(conf.Server.DataFolder, "resources")),
+	}
+}