(SP: 1) Add 'aboutStudent' field for User & update User update logic

[dudchakk]

Task description:

• [ ] enhance the User schema by adding a new field aboutStudent
• [ ] extend the logic for updating user data to handle the aboutStudent field updates

This field should align with the About the student accordion (#2684) on frontend.

The field should be an object with the following properties:

• personalIntroduction (String)
• learningGoals (String)
• learningActivities (String)

Ensure that data coming from the frontend's About the student accordion block is properly stored in the database.