seeded DDB table with some usernames.
called the RPC from Bloom with a username from the table, UpdateType = REMOVE, and valid auth token ("test"); confirmed that username was deleted from table.
called the RPC with a new username, UpdateType = ADD, and valid auth token; confirmed that username was added to table.
called the RPC with a new username, UpdateType = REMOVE, and valid auth token; got back an error as expected, since username doesn't exist in table
called the RPC with an invalid auth token; got back an error as expected