MM-57084: Use cache for GetAllProfiles (#26391)

UserStore.GetAllProfiles is a very frequent call. We cache it
when there are no options passed which is the default case.

https://mattermost.atlassian.net/browse/MM-57084

```release-note
NONE
```

server/channels/store/localcachelayer/user_layer.go

@@ -21,6 +21,8 @@ type LocalCacheUserStore struct {
 	userProfileByIdsInvalidations map[string]bool
 }
 
+const allUserKey = "ALL"
+
 func (s *LocalCacheUserStore) handleClusterInvalidateScheme(msg *model.ClusterMessage) {
 	if bytes.Equal(msg.Data, clearCacheMessageData) {
 		s.rootStore.userProfileByIdsCache.Purge()
@@ -40,8 +42,17 @@ func (s *LocalCacheUserStore) handleClusterInvalidateProfilesInChannel(msg *mode
 	}
 }
 
+func (s *LocalCacheUserStore) handleClusterInvalidateAllProfiles(msg *model.ClusterMessage) {
+	if bytes.Equal(msg.Data, clearCacheMessageData) {
+		s.rootStore.allUserCache.Purge()
+	} else {
+		s.rootStore.allUserCache.Remove(string(msg.Data))
+	}
+}
+
 func (s *LocalCacheUserStore) ClearCaches() {
 	s.rootStore.userProfileByIdsCache.Purge()
+	s.rootStore.allUserCache.Purge()
 	s.rootStore.profilesInChannelCache.Purge()
 
 	if s.rootStore.metrics != nil {
@@ -55,6 +66,7 @@ func (s *LocalCacheUserStore) InvalidateProfileCacheForUser(userId string) {
 	s.userProfileByIdsInvalidations[userId] = true
 	s.userProfileByIdsMut.Unlock()
 	s.rootStore.doInvalidateCacheCluster(s.rootStore.userProfileByIdsCache, userId, nil)
+	s.rootStore.doInvalidateCacheCluster(s.rootStore.allUserCache, allUserKey, nil)
 
 	if s.rootStore.metrics != nil {
 		s.rootStore.metrics.IncrementMemCacheInvalidationCounter("Profile By Ids - Remove")
@@ -85,6 +97,30 @@ func (s *LocalCacheUserStore) InvalidateProfilesInChannelCache(channelID string)
 	}
 }
 
+func (s *LocalCacheUserStore) GetAllProfiles(options *model.UserGetOptions) ([]*model.User, error) {
+	if isEmptyOptions(options) &&
+		options.Page == 0 && options.PerPage == 100 { // This is hardcoded to the webapp call.
+		// read from cache
+		var users []*model.User
+		if err := s.rootStore.doStandardReadCache(s.rootStore.allUserCache, allUserKey, &users); err == nil {
+			return users, nil
+		}
+
+		users, err := s.UserStore.GetAllProfiles(options)
+		if err != nil {
+			return nil, err
+		}
+
+		// populate the cache only for those options.
+		s.rootStore.doStandardAddToCache(s.rootStore.allUserCache, allUserKey, users)
+
+		return users, nil
+	}
+
+	// For any other case, simply use the store
+	return s.UserStore.GetAllProfiles(options)
+}
+
 func (s *LocalCacheUserStore) GetAllProfilesInChannel(ctx context.Context, channelId string, allowFromCache bool) (map[string]*model.User, error) {
 	if allowFromCache {
 		var cachedMap map[string]*model.User
@@ -261,3 +297,26 @@ func dedup(elements []string) []string {
 
 	return elements[:j+1]
 }
+
+func isEmptyOptions(options *model.UserGetOptions) bool {
+	// We check to see if any of the options are set or not, and then
+	// use the cache only if none are set, which is the most common case.
+	// options.WithoutTeam, Sort is unused
+	if options.InTeamId == "" &&
+		options.NotInTeamId == "" &&
+		options.InChannelId == "" &&
+		options.NotInChannelId == "" &&
+		options.InGroupId == "" &&
+		options.NotInGroupId == "" &&
+		!options.GroupConstrained &&
+		!options.Inactive &&
+		!options.Active &&
+		options.Role == "" &&
+		len(options.Roles) == 0 &&
+		len(options.ChannelRoles) == 0 &&
+		len(options.TeamRoles) == 0 &&
+		options.ViewRestrictions == nil {
+		return true
+	}
+	return false
+}