Friends

[weebao]

• From a few suggestions, we should let people add and invite friends. Honestly that'd help boost the social aspect of the app so why not?
• Should be straightforward. Add a new table friends with two foreign keys user1 and user2 which identifies them as friends. Not sure if there's better way of doing this since this would be O(2n) with n being the number of users.
• Also create an index on user1 to query friend list faster