[MM-64402] Improve validation of imported attachments (#31201)

* Improve validation of imported attachments

* Simplify multiple errors handling

* Improve logic

* Fix abs paths in tests

* Remove redundant clean

* Implement additional validation

* Fix absolute paths in test

* Add additional tests

---------

Co-authored-by: Lorenzo Gallegos <1328683+enzowritescode@users.noreply.github.com>

server/i18n/en.json

@@ -5614,6 +5614,10 @@
     "id": "app.import.profile_image.read_data.app_error",
     "translation": "Failed to read profile image data."
   },
+  {
+    "id": "app.import.validate_attachment_import_data.invalid_path.error",
+    "translation": "Failed to validate attachment import data. Invalid path: \"{{.Path}}\""
+  },
   {
     "id": "app.import.validate_bot_import_data.owner_missing.error",
     "translation": "Bot owner is missing"
@@ -5678,6 +5682,10 @@
     "id": "app.import.validate_direct_channel_import_data.unknown_favoriter.error",
     "translation": "Direct channel can only be favorited by members. \"{{.Username}}\" is not a member."
   },
+  {
+    "id": "app.import.validate_direct_post_import_data.attachment.error",
+    "translation": "Failed to validate direct post attachment data."
+  },
   {
     "id": "app.import.validate_direct_post_import_data.channel_members_required.error",
     "translation": "Missing required direct post property: channel_members"
@@ -5722,10 +5730,18 @@
     "id": "app.import.validate_emoji_import_data.image_missing.error",
     "translation": "Import emoji image field missing or blank."
   },
+  {
+    "id": "app.import.validate_emoji_import_data.invalid_image_path.error",
+    "translation": "Import emoji image field has an invalid path: \"{{.Path}}\""
+  },
   {
     "id": "app.import.validate_emoji_import_data.name_missing.error",
     "translation": "Import emoji name field missing or blank."
   },
+  {
+    "id": "app.import.validate_post_import_data.attachment.error",
+    "translation": "Failed to validate post attachment data."
+  },
   {
     "id": "app.import.validate_post_import_data.channel_missing.error",
     "translation": "Missing required Post property: Channel."
@@ -5782,6 +5798,10 @@
     "id": "app.import.validate_reaction_import_data.user_missing.error",
     "translation": "Missing required Reaction property: User."
   },
+  {
+    "id": "app.import.validate_reply_import_data.attachment.error",
+    "translation": "Failed to validate reply attachment data."
+  },
   {
     "id": "app.import.validate_reply_import_data.create_at_missing.error",
     "translation": "Missing required Reply property: create_at."
@@ -5946,6 +5966,10 @@
     "id": "app.import.validate_user_import_data.guest_roles_conflict.error",
     "translation": "User roles are not consistent with guest status."
   },
+  {
+    "id": "app.import.validate_user_import_data.invalid_image_path.error",
+    "translation": "User profile image path is invalid: \"{{.Path}}\""
+  },
   {
     "id": "app.import.validate_user_import_data.last_name_length.error",
     "translation": "User Last Name is too long."