Function member_event 

pub fn member_event(
    team_id: TeamId,
    actor_id: MemberId,
    actor_name: String,
    event_type: EventType,
    member_id: MemberId,
    member_name: String,
    member_email: Option<String>,
    role: Option<String>,
    previous_role: Option<String>,
) -> ActivityEvent

Create a member activity event