text: -- migrations/1609356128-jsonb_merge_agg.sql
  -- :up
  
  create aggregate jsonb_merge_agg(jsonb)
  (
      sfunc = jsonb_concat,
      stype = jsonb,
      initcond = '{}'
  );
  
  
  -- :down
  
  drop aggregate if exists jsonb_merge_agg(jsonb);
  