Handle "naked" CoverArtIDs (IDs of album, mediafiles and playlists)

utils/slice/slice.go

@@ -1,5 +1,13 @@
 package slice
 
+func Map[T any, R any](t []T, mapFunc func(T) R) []R {
+	r := make([]R, len(t))
+	for i, e := range t {
+		r[i] = mapFunc(e)
+	}
+	return r
+}
+
 func Group[T any, K comparable](s []T, keyFunc func(T) K) map[K][]T {
 	m := map[K][]T{}
 	for _, item := range s {

utils/slice/slice_test.go

@@ -1,6 +1,7 @@
 package slice_test
 
 import (
+	"strconv"
 	"testing"
 
 	"github.com/navidrome/navidrome/utils/slice"
@@ -13,6 +14,20 @@ func TestSlice(t *testing.T) {
 	RunSpecs(t, "Slice Suite")
 }
 
+var _ = Describe("Map", func() {
+	It("returns empty slice for an empty input", func() {
+		mapFunc := func(v int) string { return strconv.Itoa(v * 2) }
+		result := slice.Map([]int{}, mapFunc)
+		Expect(result).To(BeEmpty())
+	})
+
+	It("returns a new slice with elements mapped", func() {
+		mapFunc := func(v int) string { return strconv.Itoa(v * 2) }
+		result := slice.Map([]int{1, 2, 3, 4}, mapFunc)
+		Expect(result).To(ConsistOf("2", "4", "6", "8"))
+	})
+})
+
 var _ = Describe("Group", func() {
 	It("returns empty map for an empty input", func() {
 		keyFunc := func(v int) int { return v % 2 }