[MM-59361] custom groups & read only channels (#28892)

* added group mention, read only view and post event tracking

---------

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

server/channels/app/notification.go

@@ -869,17 +869,20 @@ func (a *App) SendNotifications(c request.CTX, post *model.Post, team *model.Tea
 				a.Srv().telemetryService.SendTelemetryForFeature(
 					telemetry.TrackGuestFeature,
 					"post_mentioned_guest",
-					map[string]any{"user_actual_id": user.Id, "post_owner_id": sender.Id},
+					map[string]any{telemetry.TrackPropertyUser: user.Id, telemetry.TrackPropertyPostAuthor: sender.Id},
 				)
 			} else if reason == DMMention {
 				a.Srv().telemetryService.SendTelemetryForFeature(
 					telemetry.TrackGuestFeature,
 					"direct_message_to_guest",
-					map[string]any{"user_actual_id": user.Id, "post_owner_id": sender.Id},
+					map[string]any{telemetry.TrackPropertyUser: user.Id, telemetry.TrackPropertyPostAuthor: sender.Id},
 				)
 			}
 		}
 	}
+	for groupId := range mentions.GroupMentions {
+		a.Srv().telemetryService.SendTelemetryForFeature(telemetry.TrackGroupsFeature, "post_mentioned_custom_group", map[string]any{telemetry.TrackPropertyUser: sender.Id, telemetry.TrackPropertyGroup: groupId, "group_size": groups[groupId].MemberCount})
+	}
 	return mentionedUsersList, nil
 }
 
@@ -1576,6 +1579,13 @@ func (a *App) insertGroupMentions(senderID string, group *model.Group, channel *
 	for _, user := range outOfChannelGroupMembers {
 		potentialGroupMembersMentioned = append(potentialGroupMembersMentioned, user.Username)
 	}
+	if len(potentialGroupMembersMentioned) != 0 {
+		a.Srv().telemetryService.SendTelemetryForFeature(
+			telemetry.TrackGroupsFeature,
+			"invite_group_to_channel__post",
+			map[string]any{telemetry.TrackPropertyUser: senderID, telemetry.TrackPropertyGroup: group.Id},
+		)
+	}
 	if mentions.OtherPotentialMentions == nil {
 		mentions.OtherPotentialMentions = potentialGroupMembersMentioned
 	} else {