[MM-23264] Get channel member counts by group (#14068)

* MM-23264 Add api endpoint for get groups with members in channel

Add store tests

Add tests for api func

Gofmt

Apply changes from code review

* MM-23264 Make store layers

* MM-23264 Check read permission on channel member counts

* Trigger CI

model/client4.go

@@ -5004,3 +5004,12 @@ func (c *Client4) PatchChannelModerations(channelID string, patch []*ChannelMode
 	defer closeBody(r)
 	return ChannelModerationsFromJson(r.Body), BuildResponse(r)
 }
+
+func (c *Client4) GetChannelMemberCountsByGroup(channelID string, includeTimezones bool, etag string) ([]*ChannelMemberCountByGroup, *Response) {
+	r, err := c.DoApiGet(c.GetChannelRoute(channelID)+"/member_counts_by_group?include_timezones="+strconv.FormatBool(includeTimezones), etag)
+	if err != nil {
+		return nil, BuildErrorResponse(r, err)
+	}
+	defer closeBody(r)
+	return ChannelMemberCountsByGroupFromJson(r.Body), BuildResponse(r)
+}