text: -- maxLength validation
  -- shorter is valid
  SELECT is_jsonb_valid('{"maxLength":2}', '"f"');
  -- exact length is valid
  SELECT is_jsonb_valid('{"maxLength":2}', '"fo"');
  -- too long is invalid
  SELECT is_jsonb_valid('{"maxLength":2}', '"foo"');
  -- ignores non-strings
  SELECT is_jsonb_valid('{"maxLength":2}', '100');
  -- two supplementary Unicode code points is long enough
  SELECT is_jsonb_valid('{"maxLength":2}', '"💩💩"');