users service: add sessions (#17744)

* users: add cache to service

* reflect review comments

app/admin.go

@@ -168,7 +168,7 @@ func (s *Server) InvalidateAllCaches() *model.AppError {
 
 func (s *Server) InvalidateAllCachesSkipSend() {
 	mlog.Info("Purging all caches")
-	s.sessionCache.Purge()
+	s.userService.ClearAllUsersSessionCacheLocal()
 	s.statusCache.Purge()
 	s.Store.Team().ClearCaches()
 	s.Store.Channel().ClearCaches()