SQL schema: user accounts

-- user_accounts.sql
CREATE TABLE accounts (
  id          UUID PRIMARY KEY DEFAULT gen_random_uuid(),
  email       TEXT NOT NULL UNIQUE,
  name        TEXT,
  tier        TEXT NOT NULL DEFAULT 'free' CHECK (tier IN ('free','basic','pro','max','enterprise')),
  created_at  TIMESTAMPTZ NOT NULL DEFAULT now(),
  updated_at  TIMESTAMPTZ NOT NULL DEFAULT now()
);

CREATE INDEX idx_accounts_email ON accounts (email);

CREATE FUNCTION set_updated_at()
RETURNS TRIGGER LANGUAGE plpgsql AS $$
BEGIN
  NEW.updated_at = now();
  RETURN NEW;
END;
$$;

CREATE TRIGGER trg_accounts_updated_at
  BEFORE UPDATE ON accounts
  FOR EACH ROW EXECUTE FUNCTION set_updated_at();