feat: add CreatedAt to albums (#159)

This change will make the GetAlbumList views with the "newest" type
work as expected.

server/ctrlsubsonic/spec/construct_by_folder.go

@@ -15,6 +15,7 @@ func NewAlbumByFolder(f *db.Album) *Album {
 		Title:      f.RightPath,
 		TrackCount: f.ChildCount,
 		Duration:   f.Duration,
+		Created:    f.CreatedAt,
 	}
 	if f.Cover != "" {
 		a.CoverID = f.SID()
@@ -28,7 +29,7 @@ func NewTCAlbumByFolder(f *db.Album) *TrackChild {
 		IsDir:     true,
 		Title:     f.RightPath,
 		ParentID:  f.ParentSID(),
-		CreatedAt: f.UpdatedAt,
+		CreatedAt: f.CreatedAt,
 	}
 	if f.Cover != "" {
 		trCh.CoverID = f.SID()

server/ctrlsubsonic/spec/construct_by_tags.go

@@ -9,7 +9,7 @@ import (
 
 func NewAlbumByTags(a *db.Album, artist *db.Artist) *Album {
 	ret := &Album{
-		Created:    a.ModifiedAt,
+		Created:    a.CreatedAt,
 		ID:         a.SID(),
 		Name:       a.TagTitle,
 		Year:       a.TagYear,

server/ctrlsubsonic/spec/spec.go

@@ -94,6 +94,7 @@ type Album struct {
 	CoverID  *specid.ID `xml:"coverArt,attr,omitempty" json:"coverArt,omitempty"`
 	ArtistID *specid.ID `xml:"artistId,attr,omitempty" json:"artistId,omitempty"`
 	Artist   string     `xml:"artist,attr,omitempty"   json:"artist,omitempty"`
+	Created  time.Time  `xml:"created,attr,omitempty"  json:"created,omitempty"`
 	// browsing by folder (eg. getAlbumList)
 	Title    string     `xml:"title,attr,omitempty"  json:"title"`
 	Album    string     `xml:"album,attr,omitempty"  json:"album"`
@@ -103,7 +104,6 @@ type Album struct {
 	Name       string        `xml:"name,attr"              json:"name"`
 	TrackCount int           `xml:"songCount,attr"         json:"songCount"`
 	Duration   int           `xml:"duration,attr"          json:"duration"`
-	Created    time.Time     `xml:"created,attr,omitempty" json:"created,omitempty"`
 	Genre      string        `xml:"genre,attr,omitempty"   json:"genre,omitempty"`
 	Year       int           `xml:"year,attr,omitempty"    json:"year,omitempty"`
 	Tracks     []*TrackChild `xml:"song,omitempty"         json:"song,omitempty"`