refactor: use ARL initialism casing

internal/deezer/client.go

@@ -31,8 +31,8 @@ func NewClient(ctx context.Context, appConfig *config.Config) (*Client, error) {
 }
 
 func resolveSession(ctx context.Context, appConfig *config.Config) (*Session, error) {
-	if appConfig.ArlCookie != "" {
-		return Authenticate(ctx, appConfig.ArlCookie)
+	if appConfig.ARLCookie != "" {
+		return Authenticate(ctx, appConfig.ARLCookie)
 	}
 
 	var session *Session

internal/deezer/session.go

@@ -71,7 +71,7 @@ func Authenticate(ctx context.Context, arlCookie string) (*Session, error) {
 	}
 
 	if res.Results.User.ID == 0 {
-		return nil, fmt.Errorf("invalid or expired arl cookie")
+		return nil, fmt.Errorf("invalid or expired ARL cookie")
 	}
 
 	opts := res.Results.User.Options