Add unit test for the `CsvContentExtractionHelper::getWordsFromCsvBackup`

[vrudas]

Add unit test for extracting Word content from the CSV files that happens on application launch. By having unit tests for this, a developer will be notified sooner when introducing breaking changes.

• good start will be extraction of CsvContentExtractionHelper::getWordsFromCsvBackup method into a dedicated Util class
• as an example/reference of desired unit tests take look at code of issue #1396