Add authorization for NestBot Calendar events.

[ahmedxgouda]

Describe the solution you'd like
Now, anyone can access the calendar events feature of NestBot. We should limit it to be used by project leaders only.

Are you going to work on implementing this?

• Yes
• No

Additional context
A user can be identified as a leader in the EntityMember model.

[tusharrrr1]

Hey @ahmedxgouda would like to work on this. assign if possible

[ahmedxgouda]

@tusharrrr1 I will work on it, you could see other open issues.