CREATE TABLE activities (
    id BIGSERIAL PRIMARY KEY,
    name VARCHAR(255) NOT NULL,
    start_time_utc TIMESTAMP NOT NULL,
    end_time_utc TIMESTAMP NOT NULL,
    target_users_config VARCHAR(2000),
    page_content_config VARCHAR(4000),
    reward_calculation_mode VARCHAR(50) NOT NULL DEFAULT 'delta',
    status VARCHAR(50) NOT NULL DEFAULT 'draft',
    created_at TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP,
    updated_at TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP
);
