CREATE TABLE IF NOT EXISTS channels (
  id            uuid        PRIMARY KEY DEFAULT gen_random_uuid(),
  community_id  uuid        REFERENCES communities (id) ON DELETE CASCADE,
  category_id   uuid        REFERENCES channel_categories (id) ON DELETE SET NULL,
  name          text        NOT NULL,
  type          text        NOT NULL CHECK (type IN ('text', 'dm', 'group_dm')),
  visibility    text        NOT NULL DEFAULT 'public' CHECK (visibility IN ('public', 'private')),
  topic         text,
  created_at    timestamptz DEFAULT now()
);