Update design doc to include about PlacementAPI

[amartyasinha]

No description provided.

[openshift-ci]

Skipping CI for Draft Pull Request.
If you want CI signal for your change, please convert it to an actual PR.
You can still manually trigger a test run with /test all

[centosinfra-prod-github-app]

Build failed (check pipeline). Post recheck (without leading slash)
to rerun all jobs. Make sure the failure cause has been resolved before
you rerun jobs.

https://gateway-cloud-softwarefactory.apps.ocp.cloud.ci.centos.org/zuul/t/rdoproject.org/buildset/843ee9c7ce854b95967b47455449c455

✔️ openstack-meta-content-provider SUCCESS in 2h 34m 15s
✔️ nova-operator-tempest-multinode SUCCESS in 2h 15m 33s
❌ nova-operator-tempest-multinode-ceph RETRY_LIMIT in 15m 31s

[amartyasinha]

recheck

[mrkisaolamb]

lgtm

[openshift-ci]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: amartyasinha, mrkisaolamb

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Details

Needs approval from an approver in each of these files:

• OWNERS [amartyasinha,mrkisaolamb]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment