CREATE OR REPLACE FUNCTION public.jsonb_array_add_distinct(_arr jsonb, _add text) RETURNS jsonb AS
$$
DECLARE
    _ret jsonb;

BEGIN

SELECT 
    jsonb_agg(DISTINCT x.ae)
INTO
    _ret
FROM
    (
        SELECT jsonb_array_elements_text(_arr) ae
        UNION ALL 
        SELECT _add ae
    ) x;

RETURN _ret;

END;
$$
language plpgsql