Add timestamp to most used collections

Title: Add Timestamp to All Collections

Description:
We need to add timestamp fields to all the specified collections in the database. This will allow us to keep track of when documents are created and when they are last modified. Additionally, we need to change the date objects to timestamps in the 'groups' collection.

Collections and Fields to be Modified:

1. user collection: #1346

   • created_at: Timestamp for the first time the document is created.
   • updated_at: Timestamp for the last time the document is modified.

2. user-status - Onboarding collection: (#1389 )

   • from: Timestamp for when the status is added to onboarding.

3. Tasks collection: #1009

   • created_at: Timestamp for the first time the document is created.
   • updated_at: Timestamp for the last time the document is modified.

4. applicants collection: https://github.com/Real-Dev-Squad/website-backend/issues/1395

   • created_at: Timestamp for the first time the document is created.
   • updated_at: Timestamp for the last time the document is modified.

5. groups collection:

   • created_at: Timestamp for the first time the document is created.
   • updated_at: Timestamp for the last time the document is modified.

Please make the necessary changes to the database schema and update the existing records accordingly. Once the modifications are done, ensure that the codebase is updated to use these new timestamp fields wherever applicable.