CREATE TABLE roles (
    id UUID PRIMARY KEY,
    name TEXT UNIQUE NOT NULL,
    description TEXT
);

CREATE TABLE groups (
    id UUID PRIMARY KEY,
    name TEXT NOT NULL,
    created_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
);

CREATE TABLE user_group_roles (
    user_id UUID NOT NULL REFERENCES users(id),
    group_id UUID NOT NULL REFERENCES groups(id),
    role_id UUID NOT NULL REFERENCES roles(id),
    granted_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
    revoked_at TIMESTAMPTZ,
    PRIMARY KEY (user_id, group_id, role_id)
);