[Feature] Notifications and Todo participants

[amoraitis]

Is your feature request related to a problem? Please describe.
It would be really beautiful to add tasks shared between users

Describe the solution you'd like
Add Participants field to TodoList entity and notifications to the ApplicationUser entity for the backend. Also, an invite button for todos would be nice, among with a notification glyph in the right menu.

Describe alternatives you've considered
Make use of the SignalR library to make it real time

[noamyogev84]

Hey @amoraitis
I'd like to take this :)

[amoraitis]

@noamyogev84 That's nice! Please feel free to start. Let me know if you need any design details, although I believe this is straightforward.

[Abhi441]

kindly give me bug I will fix it

[Abhi441]

I'd like to take this :)