The `check` decorator expects the context to be in the `kwargs`
or to be the last arguments of the method.
The `call_kw` route, which is decorated by the `check` decorator,
like every route,
expands its kwargs arguments.
Therefore, once in the `check` decorator,
the context is located in the `kwargs` key
of the kwargs.
(More simply, instead of
`kwargs.get('context', {})`
it's
`kwargs.get('kwargs', {}).get('context', {})`
As the context is not retrieved correctly,
the lang is not set correctly either,
and the sql constraints were not translated.
In 7.0, it worked, because there was a double
check, as the call_kw was called trough an rpc
(`dispatch_rpc`) call,
which was decorated by the `check` as well.
As a fix for 8.0, we apply the same logic,
we perform a double check, with an indirection.
The check decorator should probably be
refactored, but this cannot be done
in a stable release such as 8.0.
Closes#3634
bd9cbdfc41