[goal] Deprecate the JSON formatted policy file

As per the community goal of migrating the policy file
the format from JSON to YAML[1], we need to replace policy.json to
policy.yaml and remove deprecated policy.json.

config_template has been choosen instead of the copy, since it can
properly handle content that has been lookuped.

We make a separate task not to restart service when it's not needed.

[1]https://governance.openstack.org/tc/goals/selected/wallaby/migrate-policy-format-from-json-to-yaml.html

Depends-On: https://review.opendev.org/c/openstack/heat/+/766861
Change-Id: I3d1c51a025f2c94cb02f7e0882472344dcb97fa4

handlers/main.yml

@@ -22,3 +22,12 @@
   with_items: "{{ filtered_heat_services }}"
   listen:
     - "venv changed"
+
+# NOTE (noonedeadpunk): Remove this task after Xena release
+- name: Remove obsoleted policy.json
+  file:
+    path: "/etc/heat/policy.json"
+    state: absent
+  listen:
+    - "Restart heat services"
+    - "venv changed"

tasks/heat_post_install.yml

@@ -26,12 +26,27 @@
     - Restart heat services
     - Restart uwsgi services
 
-- name: Implement policy.json if there are overrides configured
-  copy:
-    content: "{{ heat_policy_overrides | to_nice_json }}"
-    dest: "/etc/heat/policy.json"
+- name: Implement policy.yaml if there are overrides configured
+  config_template:
+    content: "{{ heat_policy_overrides }}"
+    dest: "/etc/heat/policy.yaml"
+    owner: "root"
+    group: "{{ heat_system_group_name }}"
+    mode: "0640"
+    config_type: yaml
   when:
-    - heat_policy_overrides != {}
+    - heat_policy_overrides | length > 0
+  tags:
+    - heat-policy-override
+
+- name: Remove legacy policy.yaml file
+  file:
+    path: "/etc/heat/policy.yaml"
+    state: absent
+  when:
+    - heat_policy_overrides | length == 0
+  tags:
+    - heat-policy-override
 
 # NOTE(cloudnull): This is using "cp" instead of copy with a remote_source
 #                  because we only want to copy the original files once. and we