Ansible inventory generation and endpoint

One of the goals for Craton is to make generation and tracking of ansible inventory easy. It makes sense for Craton to do so since we will maintain all the inventory and variables that would be used during an Ansible run. To make this happen we need to expose an ansible inventory specific endpoint such that a user can query the endpoint (with filters) for specific region/cell/host resource and get Ansible inventory json blob back that can be used to run a playbook.

The second part of this BP is to ensure that such an inventory is fully OpenStackAnsible compatible and there ensure that we can encapsulate all the inventory and metadata items for OSA within Craton Ansible inventory logic.