Serialize complex objects in FluentFormatter
Serialize complex objects in FluentFormatter

This change introduces the serialization with basically json dumps,
falling back to repr for non-serializable object. We check the types
of the top level objects passed to the formatter, as for example
an object enclosed into dictionary passed to the logger should be a
much more rare case.

Closes-Bug: 1782361
Change-Id: Ib214f95abfadd91f85b6cce853057a572ec287f6

openstack/oslo.log