ActivityLog: target_user_uuid?: uuid

Discussion:


Q1: Add optional field: target_user_uuid for activity_log

Q2: Add method to persist user in activity log consistently?
```
ActivityLogUser = { 
userName: string <-- display name
userUuid: UUID <-- reference to users table
role?
other fields?
}


Users.getActivityLog({ user, role?, countryIso? });
```