CREATE TABLE certificates (
    certificate_id INT AUTO_INCREMENT PRIMARY KEY,
    user_id INT NOT NULL,
    valid_from DATE NOT NULL,
    valid_to DATE NOT NULL,
);
CREATE TABLE certificate_organizations (
    certificate_id INT,
    organization_id INT,
    PRIMARY KEY (certificate_id, organization_id)
);

CREATE TABLE certificate_extra_users (
	certificate_id INT,
	user_id INT,
	PRIMARY KEY (certificate_id, user_id)
);