This refactoring is in the context of the work related to moving security
tokens to a new index. In that regard, the Token Service has to work with
token documents stored in any of the two indices, albeit only as a transient
situation. I reckoned the added complexity as unmanageable,
hence this refactoring.
This is incomplete, as it fails to address the goal of minimizing .security accesses,
but I have stopped because otherwise it would've become a full blown rewrite
(if not already). I will follow-up with more targeted PRs.
In addition to being a true refactoring, some 400 errors moved to 500. Furthermore,
more stringed validation of various return result, has been implemented, notably the
one of the token document creation.
2f80b7304f