Create comment service

[MartinBenediktBusch]

Overview

This PR implements functionalities that allow to save a comment to the database and retrieve comments related to a specific question option. Important, I explicitly did not implement functionality to edit/update a comment. This is something that could be done in a further PR as it is an additional feature.

Changes Implemented

1. saveComment Function

• This function handles the process of saving a comment to the database. It calls the upsertComment function to insert or update the comment in the database.
• Upon successful insertion or update, it returns a JSON response containing the inserted/updated comment data.

2. insertComment Function

• This function performs the actual insertion or update of a comment in the database.
• It receives the database pool connection, comment data, and user ID as parameters.

3. getCommentsForOption Function

• This function retrieves comments related to a specific question option from the database.
• Upon successful retrieval, it returns a JSON response containing the retrieved comments.

[diegoalzate]

small change