MM-33708 - Add MentionCountRoot column to ChannelMembers (#17099)

* added new column for root-only mentions

Co-authored-by: Mattermod <mattermod@users.noreply.github.com>

model/team_member.go

@@ -31,10 +31,11 @@ type TeamMember struct {
 
 //msgp:ignore TeamUnread
 type TeamUnread struct {
-	TeamId       string `json:"team_id"`
-	MsgCount     int64  `json:"msg_count"`
-	MsgCountRoot int64  `json:"msg_count_root"`
-	MentionCount int64  `json:"mention_count"`
+	TeamId           string `json:"team_id"`
+	MsgCount         int64  `json:"msg_count"`
+	MentionCount     int64  `json:"mention_count"`
+	MentionCountRoot int64  `json:"mention_count_root"`
+	MsgCountRoot     int64  `json:"msg_count_root"`
 }
 
 //msgp:ignore TeamMemberForExport