-- Group chats. The server stores group METADATA (name + membership) so members
-- can discover each other, but message content is still E2E: the sender encrypts
-- each message separately to every member (pairwise Signal fan-out).

CREATE TABLE groups (
  id          TEXT PRIMARY KEY,
  name        TEXT NOT NULL,
  created_by  TEXT NOT NULL REFERENCES users(id) ON DELETE CASCADE,
  created_at  INTEGER NOT NULL
);

CREATE TABLE group_members (
  group_id  TEXT NOT NULL REFERENCES groups(id) ON DELETE CASCADE,
  user_id   TEXT NOT NULL REFERENCES users(id) ON DELETE CASCADE,
  added_at  INTEGER NOT NULL,
  PRIMARY KEY (group_id, user_id)
);
CREATE INDEX idx_group_members_user ON group_members(user_id);