[RFE] Allow custom API microversions in clouds.yaml

[Bogdan Dobrelya]

In order to support mixed controllers with computes versions, like Z+W, there would be a need to specify API microversions for generated clouds.yaml / rc files (if not deprecated for Z).

Today we have the following:
- tripleo_keystone_resources_cloud_config in t-h-t has no data source for API microversions
- in tripleo_common, those are hardcoded as:
tripleo_common/constants.py:DEFAULT_IDENTITY_API_VERSION = '3'
tripleo_common/constants.py:DEFAULT_COMPUTE_API_VERSION = '2.latest'
tripleo_common/constants.py:DEFAULT_IMAGE_API_VERSION = '2'
tripleo_common/constants.py:DEFAULT_VOLUME_API_VERSION = '3'

And there is no option for placement API microversion.

While that may be fine for non-mixed versions deployments, since users are on their own to add or drop these as their cases require, for mixed versions that seems like becomes a mandatory for deployment framework to encode it in clouds.yaml.

[Rabi Mishra (rabi)]

Not sure I understand the expectation here.

API services are in the controllers and if some api is not supported by the computes (being older release), user would/should get an appropriate error.

Normally we specify the latest major/base version in clouds.yaml or overcloudrc and the users can use --os-* with openstack commands to use a micro version for a specific api.

We're using 2.latest for nova (which is kind of a hack in openstackclient[1]) to use the latest micro version supported by the deployment.

IMO can either use the latest major/base version or the latest microversion in clouds.yaml and overcloudrc. Nothing more than that.

[1] https://github.com/openstack/python-openstackclient/commit/
> a5a343a5a86658246cc136a330eee951e32c7b56