update import/export for attachments and new file paths (#22915)

* update import/export for attachments and new file paths

* add unit test

* update templates test

* temp checking

* cleanup

* cleanup

* more cleanup

* lint fixes

* cleanup some functions

* cleanup

* fix build breaks

* fix tests for changes

* move function to different file

* more cleanup, code movement

* unit test fixes

* add unit tests

* fix tests

* more unit test fixes

* test fix

* revert package-lock.json

* fixes from code review

* fix export image

* more fixes to remove attachmentId

* change from removed api

* update test

* lint fixes

* update for review comments

* fix tests

* test fix

* lint fix

* remove sprintf from logging, use mlog

* more lint fixes

* Update server/boards/app/files.go

Co-authored-by: Doug Lauder <wiggin77@warpmail.net>

* remove code

---------

Co-authored-by: Mattermost Build <build@mattermost.com>
Co-authored-by: Doug Lauder <wiggin77@warpmail.net>

server/boards/model/file.go

@@ -0,0 +1,27 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+package model
+
+import (
+	"mime"
+	"path/filepath"
+	"strings"
+
+	"github.com/mattermost/mattermost-server/server/v8/boards/utils"
+	mm_model "github.com/mattermost/mattermost-server/server/v8/model"
+)
+
+func NewFileInfo(name string) *mm_model.FileInfo {
+
+	extension := strings.ToLower(filepath.Ext(name))
+	now := utils.GetMillis()
+	return &mm_model.FileInfo{
+		CreatorId: "boards",
+		CreateAt:  now,
+		UpdateAt:  now,
+		Name:      name,
+		Extension: extension,
+		MimeType:  mime.TypeByExtension(extension),
+	}
+
+}