feat(jellyfin): emit DateCreated (Date Added) on items

BaseItemDto had no DateCreated, so clients showed 'No Date Added' and had
nothing to sort 'Recently Added' by. Emit it as ISO 8601 from each entity's
CreatedAt (the same field the recently_added sort uses) for songs, albums
and artists.

server/jellyfin/dto/dto.go

@@ -43,16 +43,19 @@ type BaseItemDto struct {
 	// PlaylistItemId identifies this entry within a playlist listing (GET /Playlists/{id}/Items).
 	// It's only set there, and is distinct from Id so a song appearing more than once in the same
 	// playlist can be removed by occurrence (DELETE .../Items?EntryIds=...) rather than by song id.
-	PlaylistItemId       string            `json:"PlaylistItemId,omitempty"`
-	Type                 string            `json:"Type"`
-	IsFolder             bool              `json:"IsFolder"`
-	MediaType            string            `json:"MediaType,omitempty"`
-	CollectionType       string            `json:"CollectionType,omitempty"`
-	ParentId             string            `json:"ParentId,omitempty"`
-	RunTimeTicks         int64             `json:"RunTimeTicks,omitempty"`
-	IndexNumber          *int              `json:"IndexNumber,omitempty"`
-	ParentIndexNumber    *int              `json:"ParentIndexNumber,omitempty"`
-	ProductionYear       *int              `json:"ProductionYear,omitempty"`
+	PlaylistItemId    string `json:"PlaylistItemId,omitempty"`
+	Type              string `json:"Type"`
+	IsFolder          bool   `json:"IsFolder"`
+	MediaType         string `json:"MediaType,omitempty"`
+	CollectionType    string `json:"CollectionType,omitempty"`
+	ParentId          string `json:"ParentId,omitempty"`
+	RunTimeTicks      int64  `json:"RunTimeTicks,omitempty"`
+	IndexNumber       *int   `json:"IndexNumber,omitempty"`
+	ParentIndexNumber *int   `json:"ParentIndexNumber,omitempty"`
+	ProductionYear    *int   `json:"ProductionYear,omitempty"`
+	// DateCreated is the ISO 8601 date the item was added to the library; clients show it as
+	// "Date Added" and sort "Recently Added" by it.
+	DateCreated          string            `json:"DateCreated,omitempty"`
 	Album                string            `json:"Album,omitempty"`
 	AlbumId              string            `json:"AlbumId,omitempty"`
 	AlbumArtist          string            `json:"AlbumArtist,omitempty"`

server/jellyfin/dto/mappers.go

@@ -8,6 +8,15 @@ import (
 
 func TicksFromSeconds(sec float32) int64 { return int64(float64(sec) * 1e7) }
 
+// jellyfinDate formats a time as the ISO 8601 string Jellyfin clients expect for DateCreated, or
+// "" for the zero time so the field is omitted rather than sent as a meaningless epoch.
+func jellyfinDate(t *time.Time) string {
+	if t == nil || t.IsZero() {
+		return ""
+	}
+	return t.UTC().Format(time.RFC3339)
+}
+
 // channelLayout maps a channel count to the label Jellyfin clients expect on a MediaStream.
 func channelLayout(n int) string {
 	switch n {
@@ -92,6 +101,7 @@ func SongToBaseItem(mf model.MediaFile) BaseItemDto {
 		AlbumArtist:       mf.AlbumArtist,
 		Artists:           []string{mf.Artist},
 		RunTimeTicks:      TicksFromSeconds(mf.Duration),
+		DateCreated:       jellyfinDate(&mf.CreatedAt),
 		Container:         mf.Suffix,
 		CanDownload:       true,
 		BackdropImageTags: []string{},
@@ -134,6 +144,7 @@ func AlbumToBaseItem(al model.Album) BaseItemDto {
 		ChildCount:        new(al.SongCount),
 		SongCount:         new(al.SongCount),
 		RunTimeTicks:      TicksFromSeconds(al.Duration),
+		DateCreated:       jellyfinDate(&al.CreatedAt),
 		ImageTags:         map[string]string{"Primary": al.ID},
 		ImageBlurHashes:   map[string]map[string]string{"Primary": {al.ID: blurHash(al.ID)}},
 		BackdropImageTags: []string{},
@@ -162,6 +173,7 @@ func ArtistToBaseItem(ar model.Artist) BaseItemDto {
 		IsFolder:          true,
 		AlbumCount:        new(ar.AlbumCount),
 		SongCount:         new(ar.SongCount),
+		DateCreated:       jellyfinDate(ar.CreatedAt),
 		ImageTags:         map[string]string{"Primary": ar.ID},
 		ImageBlurHashes:   map[string]map[string]string{"Primary": {ar.ID: blurHash(ar.ID)}},
 		BackdropImageTags: []string{},

server/jellyfin/dto/mappers_test.go

@@ -44,6 +44,15 @@ var _ = Describe("mappers", func() {
 		Expect(item.ImageBlurHashes).To(BeNil())
 	})
 
+	It("sets DateCreated from the media file's CreatedAt", func() {
+		mf := model.MediaFile{ID: "s1", Title: "Song", CreatedAt: time.Date(2024, 1, 15, 10, 30, 0, 0, time.UTC)}
+		Expect(SongToBaseItem(mf).DateCreated).To(Equal("2024-01-15T10:30:00Z"))
+	})
+
+	It("omits DateCreated when CreatedAt is the zero time", func() {
+		Expect(SongToBaseItem(model.MediaFile{ID: "s1", Title: "Song"}).DateCreated).To(BeEmpty())
+	})
+
 	It("builds a MediaSourceInfo from a media file", func() {
 		mf := model.MediaFile{ID: "s1", Size: 5242880, Suffix: "mp3", BitRate: 320, Duration: 100}
 		src := MediaSourceFromMediaFile(mf)

server/jellyfin/e2e/browsing_test.go

@@ -2,6 +2,7 @@ package e2e
 
 import (
 	"net/http"
+	"time"
 
 	"github.com/navidrome/navidrome/server/jellyfin/dto"
 	. "github.com/onsi/ginkgo/v2"
@@ -165,6 +166,14 @@ var _ = Describe("Browsing", func() {
 			Expect(item.Type).To(Equal("Audio"))
 		})
 
+		It("includes a parseable DateCreated (Date Added) on a song", func() {
+			var item dto.BaseItemDto
+			parseInto(get("/Items/"+enc(songID("So What"))), &item)
+			Expect(item.DateCreated).ToNot(BeEmpty())
+			_, err := time.Parse(time.RFC3339, item.DateCreated)
+			Expect(err).ToNot(HaveOccurred())
+		})
+
 		It("resolves an artist", func() {
 			var item dto.BaseItemDto
 			parseInto(get("/Items/"+enc(artistID("Miles Davis"))), &item)