CREATE TABLE IF NOT EXISTS users (
    id SERIAL PRIMARY KEY,
    username TEXT NOT NULL UNIQUE,
    password TEXT NOT NULL,
    email TEXT,
    created_at TIMESTAMPTZ DEFAULT now()
);

CREATE TABLE IF NOT EXISTS identities (
    id SERIAL PRIMARY KEY,
    user_id INTEGER REFERENCES users(id) ON DELETE CASCADE,
    provider TEXT NOT NULL,
    external_id TEXT NOT NULL,
    UNIQUE(provider, external_id)
);

CREATE TABLE IF NOT EXISTS sessions (
    id SERIAL PRIMARY KEY,
    user_id INTEGER REFERENCES users(id) ON DELETE CASCADE,
    token TEXT NOT NULL,
    expires_at TIMESTAMPTZ NOT NULL
);