Comment 2 for bug 1730329

Reviewed: https://review.openstack.org/517894
Committed: https://git.openstack.org/cgit/openstack/oslo.log/commit/?id=1b012d0fc6811f00e032e52ed586fe37e157584d
Submitter: Zuul
Branch: master

commit 1b012d0fc6811f00e032e52ed586fe37e157584d
Author: Juan Antonio Osorio Robles <email address hidden>
Date: Mon Nov 6 08:59:43 2017 +0000

    Capture context in its own key for JSON-based formatters

    The JSON formatter used to rely on services making their logging calls
    and passing the context there. A call it expted would be

        LOG.debug("Some message", context=context)

    This would end up in the "extra" section of the logging record. This is
    not usually the case, as projects don't always pass the context on that
    call. This also applies to the Fluent formatter which is based on the
    JSON one.

    For the JSON formatter, we already are getting the context from the
    record. So lets use that if no context was provided in the record's
    'extra' section. Finally, this places the context in its own section,
    which is named 'context'.

    Closes-Bug: #1730329
    Depends-On: I2b245c1665c3587be3c476b803122788d186e5d5
    Change-Id: I765dae17d2ecadce1672f16e432e748d5233acf8