@VisibleForTesting
  static ByteString getFullSearchKeyByteString(final byte prefix, final byte[] searchKeyBytes) {
    final ByteBuffer fullSearchKeyBuffer = ByteBuffer.allocate(searchKeyBytes.length + 1);
    fullSearchKeyBuffer.put(prefix);
    fullSearchKeyBuffer.put(searchKeyBytes);
    fullSearchKeyBuffer.flip();

    return ByteString.copyFrom(fullSearchKeyBuffer.array());
  }
@Test
  void getFullSearchKey() {
    final byte[] charBytes = new byte[]{KeyTransparencyController.ACI_PREFIX};
    final byte[] aci = ACI.toCompactByteArray();

    final byte[] expectedFullSearchKey = new byte[aci.length + 1];
    System.arraycopy(charBytes, 0, expectedFullSearchKey, 0, charBytes.length);
    System.arraycopy(aci, 0, expectedFullSearchKey, charBytes.length, aci.length);

    assertArrayEquals(expectedFullSearchKey,
        KeyTransparencyController.getFullSearchKeyByteString(KeyTransparencyController.ACI_PREFIX, aci).toByteArray());
  }