[oslo] Specs proposal to use cotyledon and futurist.

Hi there,

Further to my previous mail, I have decided to create a specs proposal[1] within oslo. The idea is to use cotyledon and futurist in oslo.service and not to deprecate the project. Please don't hesitate to send me feedback.

[1] https://review.opendev.org/c/openstack/oslo-specs/+/922597