c5e59b5e9e
As per the community goal of migrating the policy file the format from JSON to YAML[1], we need to do two things: 1. Change the default value of '[oslo_policy] policy_file'' config option from 'policy.json' to 'policy.yaml' with upgrade checks. 2. Deprecate the JSON formatted policy file on the project side via warning in doc and releasenotes. [1]https://governance.openstack.org/tc/goals/selected/wallaby/migrate-policy-format-from-json-to-yaml.html Change-Id: I8b78c7b640ab18ddfc809cb4603decc739d494d1