ALTER TABLE oauth2_consent_session
    DROP FOREIGN KEY oauth2_consent_session_subject_fkey,
    ADD CONSTRAINT oauth2_consent_subject_fkey
        FOREIGN KEY (subject)
            REFERENCES user_opaque_identifier (identifier) ON UPDATE RESTRICT ON DELETE RESTRICT;

DELETE FROM oauth2_consent_session
WHERE subject IS NULL;

ALTER TABLE oauth2_consent_session
    MODIFY subject CHAR(36) NOT NULL;