feat(backend/repositories): add get tags by file method

refactor(backend/domain): start switching from pgx types

backend/internal/infrastructure/persistence/postgres/file_repository.go

@@ -270,3 +270,44 @@ func (s *FileRepository) Delete(ctx context.Context, user_id int, file_id string
 	}
 	return
 }
+
+func (s *FileRepository) GetTags(ctx context.Context, user_id int, file_id string) (tags []domain.TagItem, domainErr *domain.DomainError) {
+	rows, err := s.db.Query(ctx, `
+		SELECT
+			t.id,
+			t.name,
+			t.color,
+			c.id,
+			c.name,
+			c.color
+		FROM data.tags t
+		LEFT JOIN data.categories c ON c.id=t.category_id
+		JOIN data.file_tag ft ON ft.tag_id=t.id AND ft.file_id=$2
+		JOIN data.files f ON f.id=$2
+		WHERE NOT f.is_deleted AND (f.creator_id=$1 OR (SELECT view FROM acl.files WHERE file_id=$2 AND user_id=$1) OR (SELECT is_admin FROM system.users WHERE id=$1))
+		`, user_id, file_id)
+	if err != nil {
+		var pgErr *pgconn.PgError
+		if errors.As(err, &pgErr) && (pgErr.Code == "22P02" || pgErr.Code == "22007") {
+			domainErr = domain.NewDomainError(err, domain.ErrValidation, "format", pgErr.Message)
+			return
+		}
+		domainErr = domain.NewUnexpectedError(err)
+		return
+	}
+	defer rows.Close()
+	for rows.Next() {
+		var tag domain.TagItem
+		err = rows.Scan(&tag.ID, &tag.Name, &tag.Color, &tag.Category.ID, &tag.Category.Name, &tag.Category.Color)
+		if err != nil {
+			domainErr = domain.NewUnexpectedError(err)
+			return
+		}
+		tags = append(tags, tag)
+	}
+	err = rows.Err()
+	if err != nil {
+		domainErr = domain.NewUnexpectedError(err)
+	}
+	return
+}