Support attachments in post and replies - Bulk import (#9124)

* 9006 - process the attachments of the post

* 9006 enabling the import of attachments in the reply post

* 9006 assert if the post and files are linked

* 9006 fixed the typo

i18n/en.json

@@ -2926,6 +2926,14 @@
     "id": "app.import.validate_user_teams_import_data.team_name_missing.error",
     "translation": "Team name missing from User's Team Membership."
   },
+  {
+    "id": "app.import.attachment.bad_file.error",
+    "translation": "Error reading the file at: \"{{.FilePath}}\""
+  },
+  {
+    "id": "app.import.attachment.file_upload.error",
+    "translation": "Error uploading the file: \"{{.FilePath}}\""
+  },
   {
     "id": "app.notification.body.intro.direct.full",
     "translation": "You have a new Direct Message."