I came up with this:
```sql
BEGIN;

ALTER TYPE user_timeline_event_type_enum ADD VALUE 'thanks' AFTER 'personal_recording_recommendation';

CREATE TYPE thank_user_timeline_event_type_enum AS ENUM('recording_recommendation', 'recording_pin', 'personal_recording_recommendation');

CREATE TABLE thank_user_timeline_event (
    id           SERIAL NOT NULL,  --PK
    user_id      INTEGER NOT NULL, --FK to "user"
    recording_id INTEGER NOT NULL, --FK to ""
    event_type   thank_user_timeline_event_type_enum NOT NULL,
    event_id     INTEGER NOT NULL, --Row ID of recommendation or pin
    created      TIMESTAMP WITH TIME ZONE DEFAULT NOW() NOT NULL,
    msg          TEXT
);

ALTER TABLE thank_user_timeline_event
    ADD CONSTRAINT thank_user_timeline_event_pkey
    PRIMARY KEY (id);

ALTER TABLE thank_user_timeline_event
    ADD CONSTRAINT thank_user_timeline_event_user_id_foreign_key
    FOREIGN KEY (user_id)
    REFERENCES "user" (id)
    ON DELETE CASCADE;

CREATE UNIQUE INDEX user_id_event_type_event_id_ndx_thank_user_timeline_event ON thank_user_timeline_event (user_id, event_type, event_id);

COMMIT;
```

but what should I put in foreign key to recording_id?
As we want to thank a particular personal recommendation, pin or recommendation to followers right?
or this row shouldnt be there?