[FEATURE]Event in calendar

[SmallBeahan]

Is your feature request related to a problem? Please describe.
I'd like to be able to add a meeting for certain people involved in a project, with a date and time, so that everyone can see it in the project calendar, and in their personal calendar. But there's nothing.

Describe the solution you'd like
I'd like to be able to create a meeting or event in the project calendar (milestone), with participants, a date, a time, a title and a description. I'd also like a notification to be sent.

Maybe an invitation?