CREATE TABLE IF NOT EXISTS files (
    id serial,
    file_id varchar(255) not null unique,
    file_name varchar(255) not null,
    valid_till timestamp not null,
    kind varchar(255) not null,
    primary key (id)
);

ALTER TABLE files ADD COLUMN IF NOT EXISTS delete_on_download boolean;
ALTER TABLE files ALTER COLUMN delete_on_download set not null;
ALTER TABLE files ALTER COLUMN valid_till TYPE timestamptz;