[Enhancement] Backend: automatically detect event status

[infinity1729]

Description
Currently we are sending a status field in the API where admin has to manually update the status.
This issue aims to automate this by getting current dat and then pass wether it is ongoing, upcoming, or ended.

Screenshots
API call

Present code (backend/events/models.py)

Important Note:
We expect you to create a new branch for solving this issue names as eventStatus.
The command to create and access new branch is git checkout -b eventStatus

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