MM42267: Add member count in the browse channel modal (#23800)

* add base for calling the endpoint

* add endpoint and handler

* update store and layers

* call the endpoint

* align types

* update app layers

* generate mocks

* complete handler

* finish store query

* add todos

* add ui for member count

* add selector

* add a todo

* add cache layer

* optimize calls in FE

* handle invalidation of the cache

* fix go style

* fix test

* use existing channel layer count

* fix import error

* delete unnecessary code

* write tests for channel cache layer

* fix testname

* fix mocks

* fix cache layer test

* fix a test

* really fix the test

* write more tests for server

* address PR comments

* remove comment

* rename more_channels to browse_channels

* fix style

* update snapshot

* add translations

* Revert "add translations"

This reverts commit 56476a5dabe357703ef02be9a38b3e88f5c8b1e7.

* add only related translations

* address PR review points

* add test

* fix test

---------

Co-authored-by: Mattermost Build <build@mattermost.com>

server/public/model/client4.go

@@ -3047,6 +3047,21 @@ func (c *Client4) GetChannelStats(ctx context.Context, channelId string, etag st
 	return &stats, BuildResponse(r), nil
 }
 
+// GetChannelsMemberCount get channel member count for a given array of channel ids
+func (c *Client4) GetChannelsMemberCount(ctx context.Context, channelIDs []string) (map[string]int64, *Response, error) {
+	route := c.channelsRoute() + "/stats/member_count"
+	r, err := c.DoAPIPost(ctx, route, ArrayToJSON(channelIDs))
+	if err != nil {
+		return nil, BuildResponse(r), err
+	}
+	defer closeBody(r)
+	var counts map[string]int64
+	if err := json.NewDecoder(r.Body).Decode(&counts); err != nil {
+		return nil, nil, NewAppError("GetChannelsMemberCount", "api.unmarshal_error", nil, "", http.StatusInternalServerError).Wrap(err)
+	}
+	return counts, BuildResponse(r), nil
+}
+
 // GetChannelMembersTimezones gets a list of timezones for a channel.
 func (c *Client4) GetChannelMembersTimezones(ctx context.Context, channelId string) ([]string, *Response, error) {
 	r, err := c.DoAPIGet(ctx, c.channelRoute(channelId)+"/timezones", "")

server/public/model/cluster_message.go

@@ -29,6 +29,7 @@ const (
 	ClusterEventInvalidateCacheForChannelFileCount          ClusterEvent = "inv_channel_file_count"
 	ClusterEventInvalidateCacheForChannelPinnedpostsCounts  ClusterEvent = "inv_channel_pinnedposts_counts"
 	ClusterEventInvalidateCacheForChannelMemberCounts       ClusterEvent = "inv_channel_member_counts"
+	ClusterEventInvalidateCacheForChannelsMemberCount       ClusterEvent = "inv_channels_member_count"
 	ClusterEventInvalidateCacheForLastPosts                 ClusterEvent = "inv_last_posts"
 	ClusterEventInvalidateCacheForLastPostTime              ClusterEvent = "inv_last_post_time"
 	ClusterEventInvalidateCacheForPostsUsage                ClusterEvent = "inv_posts_usage"