Mistral serialiser and deserialiser can only work with entities in utf-8

[Anastasia Kuznetsova]

During following bug https://bugs.launchpad.net/mistral/+bug/1667415 fixing it was occurred that
there is no way to pass and process needed encoding parameter in Mistral serialiser and deserialiser.

For example, if action result is presented not in utf-8 encoding, that we will get error during its serialisation.

As a temporary workaround, there was proceed a decision to transform result from its encoding to UTF-8, but it is not a good solution from performance point of view.

So need to refactor serialiser and deserialiser to have an ability to work with any entity in any encoding.

[Dougal Matthews (d0ugal)]

Mistral serialises the result to JSON, which must be UTF-8[1]

   JSON text exchanged between systems that are not part of a closed
   ecosystem MUST be encoded using UTF-8 [RFC3629]

Therefore, closing this as Invalid.

[1]: https://tools.ietf.org/html/rfc8259#section-8.1

[OpenStack Infra (hudson-openstack)]

Related fix proposed to branch: master
Review: https://review.openstack.org/587081

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/587081
Committed: https://git.openstack.org/cgit/openstack/mistral/commit/?id=36050224ee83a14cb4c4f7ff0b80fef804fbe86c
Submitter: Zuul
Branch: master

commit 36050224ee83a14cb4c4f7ff0b80fef804fbe86c
Author: PrivateRookie <email address hidden>
Date: Mon Jul 30 21:55:29 2018 +0800

    remove invalid todo comment

    remove invalid todo comment in std_actions.py, since there is no
    need to implement this feature.

    Change-Id: I500312bb039260853a4d96a54c3395992947b9d5
    Related-Bug:#1676411