Added CORS support to Heat

[OpenStack Infra]

https://review.openstack.org/237070

Dear documentation bug triager. This bug was created here because we did not know how to map the project name "openstack/heat" to a launchpad project name. This indicates that the notify_impact config needs tweaks. You can ask the OpenStack infra team (#openstack-infra on freenode) for help if you need to.

commit 1d94dd4f2a2971e0a7dfff21a27b3f44b2cb8a0e
Author: Michael Krotscheck <email address hidden>
Date: Mon Oct 19 09:15:26 2015 -0700

    Added CORS support to Heat

    This adds the CORS support middleware to Heat, allowing a deployer
    to optionally configure rules under which a javascript client may
    break the single-origin policy and access the API directly.

    For heat, the paste.ini method of deploying the middleware was
    chosen, because it needs to be able to annotate responses created
    by keystonemiddleware. If the middleware were explicitly included
    as in the previous patch, keystone would reject the request before
    the cross-domain headers could be annotated, resulting in an
    error response that was unreadable by the user agent.

    OpenStack CrossProject Spec:
       http://specs.openstack.org/openstack/openstack-specs/specs/cors-support.html
    Oslo_Middleware Docs:
       http://docs.openstack.org/developer/oslo.middleware/cors.html
    OpenStack Cloud Admin Guide:
       http://docs.openstack.org/admin-guide-cloud/cross_project_cors.html docimpact

    Change-Id: I185f0d9f85617dd2f482cac4994ccc0a4cb6cf16

[Tom Fifield (fifieldt)]

autogenerate-config-docs could pick this up