[MM-37013] Async job to fix CRT channel unreads (#18340)

Summary
The addition of the TotalMsgCountRoot and MsgCountRoot columns to support CRT caused several issues with previously read threads and channels being marked as unread. Previously we attempted to fix this purely in a SQL migration [MM-35345][MM-35494] fixes for incorrect mentions and unreads for threads and channels #17803 but that turned out to be too heavy and it was decided to break up some of the fixes into async jobs.
This PR implements an async job to mark channels as read if there are no user posts since the last time the user viewed the channel. 

Ticket Link
https://mattermost.atlassian.net/browse/MM-37013

store/sqlstore/channel_store.go

@@ -2128,7 +2128,7 @@ func (s SqlChannelStore) GetMemberCountsByGroup(ctx context.Context, channelID s
 
 	if includeTimezones {
 		if s.DriverName() == model.DatabaseDriverMysql {
-			selectStr += `, 
+			selectStr += `,
 				COUNT(DISTINCT
 				(
 					CASE WHEN Timezone->"$.useAutomaticTimezone" = 'true' AND LENGTH(JSON_UNQUOTE(Timezone->"$.automaticTimezone")) > 0
@@ -2138,7 +2138,7 @@ func (s SqlChannelStore) GetMemberCountsByGroup(ctx context.Context, channelID s
 					END
 				)) AS ChannelMemberTimezonesCount`
 		} else if s.DriverName() == model.DatabaseDriverPostgres {
-			selectStr += `, 
+			selectStr += `,
 				COUNT(DISTINCT
 				(
 					CASE WHEN Timezone->>'useAutomaticTimezone' = 'true' AND length(Timezone->>'automaticTimezone') > 0
@@ -3753,3 +3753,32 @@ func (s SqlChannelStore) GetTeamForChannel(channelID string) (*model.Team, error
 	}
 	return &team, nil
 }
+
+func (s SqlChannelStore) GetCRTUnfixedChannelMembershipsAfter(channelID, userID string, count int) ([]model.ChannelMember, error) {
+	// we want both channelID and userID, or neither of them specified
+	if (userID == "" || channelID == "") && (channelID != userID) {
+		return nil, fmt.Errorf("channelID=%q userID=%q, got one empty param, both need to be empty or specified", channelID, userID)
+	}
+	getUnfixedCMQuery := `
+			SELECT ChannelMembers.*
+			FROM ChannelMembers, Channels
+			WHERE ChannelId = Id AND (ChannelMembers.UserId, ChannelMembers.ChannelId) > (:userId, :channelId) AND Channels.TotalMsgCountRoot > ChannelMembers.MsgCountRoot
+			ORDER BY UserId, ChannelId
+			LIMIT :count;
+	`
+	if userID == "" && channelID == "" {
+		getUnfixedCMQuery = `
+			SELECT ChannelMembers.*
+			FROM ChannelMembers, Channels
+			WHERE ChannelId = Id AND Channels.TotalMsgCountRoot > ChannelMembers.MsgCountRoot
+			ORDER BY UserId, ChannelId
+			LIMIT :count;
+		`
+	}
+	var cms []model.ChannelMember
+
+	if _, err := s.GetReplica().Select(&cms, getUnfixedCMQuery, map[string]interface{}{"channelId": channelID, "userId": userID, "count": count}); err != nil {
+		return nil, errors.Wrapf(err, "failed to %d ChannelMembers after channelId=%q and userId=%q", count, channelID, userID)
+	}
+	return cms, nil
+}

store/sqlstore/post_store.go

@@ -2522,3 +2522,22 @@ func (s *SqlPostStore) updateThreadsFromPosts(transaction *gorp.Transaction, pos
 	}
 	return nil
 }
+
+// GetUniquePostTypesSince returns the unique post types in a channel after the given timestamp
+func (s *SqlPostStore) GetUniquePostTypesSince(channelId string, timestamp int64) ([]string, error) {
+	query, args, err := s.getQueryBuilder().
+		Select("DISTINCT Type").
+		From("Posts").
+		Where(sq.And{
+			sq.Eq{"ChannelId": channelId},
+			sq.GtOrEq{"CreateAt": timestamp},
+		}).ToSql()
+	if err != nil {
+		return nil, err
+	}
+	var types []string
+	if _, err := s.GetReplica().Select(&types, query, args...); err != nil {
+		return nil, err
+	}
+	return types, nil
+}