text: CREATE TABLE IF NOT EXISTS users (
     user_id VARCHAR UNIQUE NOT NULL,
     slack_user_id VARCHAR NOT NULL, 
     slack_channel_id VARCHAR NOT NULL,
     PRIMARY KEY (user_id)
  );
  
  CREATE TABLE IF NOT EXISTS repositories (
     repository_id VARCHAR UNIQUE NOT NULL,
     owner VARCHAR NOT NULL, 
     repository VARCHAR NOT NULL,
     PRIMARY KEY (repository_id)
  );
  
  CREATE TABLE IF NOT EXISTS subscriptions (
     user_id VARCHAR NOT NULL,
     repository_id VARCHAR NOT NULL, 
     TBD VARCHAR NOT NULL
  );