refactor(mail): IMAP and the webmail read folders and messages through one MailStore

The folder list and the message list were two queries over the same tables. IMAP
took a folder's message count from a cached column and the webmail counted rows,
so the two could disagree. Both now ask MailStore, which counts the messages.

services/protocols/internal/infrastructure/postgres/message_query_repository.go

@@ -8,37 +8,26 @@ import (
 	"lambdamail/protocols/internal/application/port"
 )
 
-// MessageQueryRepository implements port.MessageQueryRepository against Postgres.
+// MessageQueryRepository lists a folder's messages for IMAP FETCH, through the
+// same MailStore listing the webmail uses.
 type MessageQueryRepository struct {
-	pool *pgxpool.Pool
+	store *MailStore
 }
 
 func NewMessageQueryRepository(pool *pgxpool.Pool) *MessageQueryRepository {
-	return &MessageQueryRepository{pool: pool}
+	return &MessageQueryRepository{store: NewMailStore(pool)}
 }
 
 func (r *MessageQueryRepository) ListMessages(ctx context.Context, folderID string) ([]port.MessageRecord, error) {
-	rows, err := r.pool.Query(ctx, `
-		SELECT m.uid, m.blob_id, m.size_bytes, m.received_at, m.modseq,
-		       COALESCE(array_agg(f.flag) FILTER (WHERE f.flag IS NOT NULL), '{}')
-		FROM email_messages m
-		LEFT JOIN message_flags f ON f.message_id = m.id AND f.received_at = m.received_at
-		WHERE m.folder_id = $1 AND m.expunged_at IS NULL
-		GROUP BY m.uid, m.blob_id, m.size_bytes, m.received_at, m.modseq
-		ORDER BY m.uid ASC
-	`, folderID)
+	messages, err := r.store.Messages(ctx, folderID, MessageQuery{})
 	if err != nil {
 		return nil, err
 	}
-	defer rows.Close()
-
 	var out []port.MessageRecord
-	for rows.Next() {
-		var rec port.MessageRecord
-		if err := rows.Scan(&rec.UID, &rec.BlobID, &rec.SizeBytes, &rec.ReceivedAt, &rec.ModSeq, &rec.Flags); err != nil {
-			return nil, err
-		}
-		out = append(out, rec)
+	for _, m := range messages {
+		out = append(out, port.MessageRecord{
+			UID: m.UID, BlobID: m.BlobID, SizeBytes: m.Size, ReceivedAt: m.ReceivedAt, Flags: m.Flags, ModSeq: m.ModSeq,
+		})
 	}
-	return out, rows.Err()
+	return out, nil
 }