Mark users as testers

I have a few more testers from Contus to verify production build. However, showing those testers in the My Psychics list is not good. We could implement this in phases:

1. In the backend database, add a new column like 'is_tester' with default value of false.

2. In the middle tier, return My Psychics list based on whether current user is a tester or not. If not, exclude the tester psychics. If yes, include the tester psychics.

The above tasks should be pretty simple. Initially we can manually set the is_tester flag without UI tool. Later on, we can enhance:

1. In webadmin Users management, allow admin to toggle a user as a tester or not.

2. If a tester consumer, bypass the requirement of a subscription to make a call.