fix(subsonic): fix JukeboxRole logic in GetUser and eliminate code duplication (#4170)

- Fix GetUser JukeboxRole to properly respect AdminOnly setting

- Extract buildUserResponse helper to eliminate duplication between GetUser and GetUsers

- Fix username field inconsistency (GetUsers was using loggedUser.Name instead of UserName)

- Add comprehensive tests covering jukebox role permissions and consistency between methods

Fixes #4160

server/subsonic/users.go

@@ -4,26 +4,40 @@ import (
 	"net/http"
 
 	"github.com/navidrome/navidrome/conf"
+	"github.com/navidrome/navidrome/model"
 	"github.com/navidrome/navidrome/model/request"
 	"github.com/navidrome/navidrome/server/subsonic/responses"
 )
 
+// buildUserResponse creates a User response object from a User model
+func buildUserResponse(user model.User) responses.User {
+	userResponse := responses.User{
+		Username:          user.UserName,
+		AdminRole:         user.IsAdmin,
+		Email:             user.Email,
+		StreamRole:        true,
+		ScrobblingEnabled: true,
+		DownloadRole:      conf.Server.EnableDownloads,
+		ShareRole:         conf.Server.EnableSharing,
+	}
+
+	if conf.Server.Jukebox.Enabled {
+		userResponse.JukeboxRole = !conf.Server.Jukebox.AdminOnly || user.IsAdmin
+	}
+
+	return userResponse
+}
+
 // TODO This is a placeholder. The real one has to read this info from a config file or the database
 func (api *Router) GetUser(r *http.Request) (*responses.Subsonic, error) {
 	loggedUser, ok := request.UserFrom(r.Context())
 	if !ok {
 		return nil, newError(responses.ErrorGeneric, "Internal error")
 	}
+
 	response := newResponse()
-	response.User = &responses.User{}
-	response.User.Username = loggedUser.UserName
-	response.User.AdminRole = loggedUser.IsAdmin
-	response.User.Email = loggedUser.Email
-	response.User.StreamRole = true
-	response.User.ScrobblingEnabled = true
-	response.User.DownloadRole = conf.Server.EnableDownloads
-	response.User.ShareRole = conf.Server.EnableSharing
-	response.User.JukeboxRole = conf.Server.Jukebox.Enabled
+	user := buildUserResponse(loggedUser)
+	response.User = &user
 	return response, nil
 }
 
@@ -32,17 +46,8 @@ func (api *Router) GetUsers(r *http.Request) (*responses.Subsonic, error) {
 	if !ok {
 		return nil, newError(responses.ErrorGeneric, "Internal error")
 	}
-	user := responses.User{}
-	user.Username = loggedUser.Name
-	user.AdminRole = loggedUser.IsAdmin
-	user.Email = loggedUser.Email
-	user.StreamRole = true
-	user.ScrobblingEnabled = true
-	user.DownloadRole = conf.Server.EnableDownloads
-	user.ShareRole = conf.Server.EnableSharing
-	if conf.Server.Jukebox.Enabled {
-		user.JukeboxRole = !conf.Server.Jukebox.AdminOnly || loggedUser.IsAdmin
-	}
+
+	user := buildUserResponse(loggedUser)
 	response := newResponse()
 	response.Users = &responses.Users{User: []responses.User{user}}
 	return response, nil