[PM-7304] Add missing i18n keys for import errors (#8743)

* Add static error message when import fails

* Adding missing string on CLI for unassigned items

* Added missing string on setImportTarget

* fixed tests

apps/cli/src/locales/en/messages.json

@@ -49,5 +49,14 @@
   },
   "unsupportedEncryptedImport": {
     "message": "Importing encrypted files is currently not supported."
+  },
+  "importUnassignedItemsError": {
+    "message": "File contains unassigned items."
+  },
+  "errorAssigningTargetCollection": {
+    "message": "Error assigning target collection."
+  },
+  "errorAssigningTargetFolder": {
+    "message": "Error assigning target folder."
   }
 }