CREATE TABLE activities (
    id BIGSERIAL PRIMARY KEY,
    name VARCHAR(255) NOT NULL,
    start_time_utc TIMESTAMP WITH TIME ZONE NOT NULL,
    end_time_utc TIMESTAMP WITH TIME ZONE NOT NULL,
    target_users_config JSONB,
    page_content_config JSONB,
    reward_calculation_mode VARCHAR(50) NOT NULL DEFAULT 'delta',
    status VARCHAR(50) NOT NULL DEFAULT 'draft',
    created_at TIMESTAMP WITH TIME ZONE NOT NULL DEFAULT NOW(),
    updated_at TIMESTAMP WITH TIME ZONE NOT NULL DEFAULT NOW()
);
