Convert all Subsonic API ints to int32 as per specification (#2252)

* Fix Genre

* Fix ArtistID3

* Fix AlbumID3

* Fix Child

* Fix NowPlayingEntry

* Fix Playlist

* Fix Share

* Fix User

* Fix Artist

* Fix Directory

* Fix Error

server/subsonic/responses/responses_test.go

@@ -215,7 +215,7 @@ var _ = Describe("Responses", func() {
 		Context("with data", func() {
 			BeforeEach(func() {
 				response.User.Email = "navidrome@deluan.com"
-				response.User.Folder = []int{1}
+				response.User.Folder = []int32{1}
 			})
 
 			It("should match .XML", func() {
@@ -247,7 +247,7 @@ var _ = Describe("Responses", func() {
 				u := User{Username: "deluan"}
 				u.Email = "navidrome@deluan.com"
 				u.AdminRole = true
-				u.Folder = []int{1}
+				u.Folder = []int32{1}
 				response.Users = &Users{User: []User{u}}
 			})