feature: action to register a separate region's endpoints for multi-region usage

[Nobuto Murata]

When considering multi-region OpenStack deployment, it's convenient if one keystone handle endpoints list of more than 2 regions. Since those two regions may be managed by completely different models and/or controllers, it would be nice if keystone charm has an action to register additional endpoints by hand by the operator.

[Corey Bryant (corey.bryant)]

Thanks Nobuto. This sounds like a reasonable feature and an action sounds like a good way to solve this.