Tuleap internal API exposes Tuleap\Cryptography\ConcealedString to handle string that are sensitive (e.g. password, token, encryption key...).

However there is a few things that can be improved:
* nothing is done to try to wipe the secret from the memory
* a ConcealedString instance can be serialized which inadvertently the secret can end up in places it should not. This particularly easy to achieve by inadvertence by putting a ConcealedString in session (the secret might be stored in cleartext in a remote Redis instance).