[management] fetch all users data from external cache in one request (#5104)

---------

Co-authored-by: pascal <pascal@netbird.io>

management/server/cache/idp.go

@@ -26,6 +26,8 @@ type UserDataCache interface {
 	Get(ctx context.Context, key string) (*idp.UserData, error)
 	Set(ctx context.Context, key string, value *idp.UserData, expiration time.Duration) error
 	Delete(ctx context.Context, key string) error
+	GetUsers(ctx context.Context, key string) ([]*idp.UserData, error)
+	SetUsers(ctx context.Context, key string, users []*idp.UserData, expiration time.Duration) error
 }
 
 // UserDataCacheImpl is a struct that implements the UserDataCache interface.
@@ -51,6 +53,29 @@ func (u *UserDataCacheImpl) Delete(ctx context.Context, key string) error {
 	return u.cache.Delete(ctx, key)
 }
 
+func (u *UserDataCacheImpl) GetUsers(ctx context.Context, key string) ([]*idp.UserData, error) {
+	var users []*idp.UserData
+	v, err := u.cache.Get(ctx, key, &users)
+	if err != nil {
+		return nil, err
+	}
+
+	switch v := v.(type) {
+	case []*idp.UserData:
+		return v, nil
+	case *[]*idp.UserData:
+		return *v, nil
+	case []byte:
+		return unmarshalUserData(v)
+	}
+
+	return nil, fmt.Errorf("unexpected type: %T", v)
+}
+
+func (u *UserDataCacheImpl) SetUsers(ctx context.Context, key string, users []*idp.UserData, expiration time.Duration) error {
+	return u.cache.Set(ctx, key, users, store.WithExpiration(expiration))
+}
+
 // NewUserDataCache creates a new UserDataCacheImpl object.
 func NewUserDataCache(store store.StoreInterface) *UserDataCacheImpl {
 	simpleCache := cache.New[any](store)