Ability to override catalog URL, fix #341

[drzraf]

Sample $options that can be passed to Openstack\Openstack (in YAML):

                catalog_overrides:
                    - name: swift
                      type: object-store
                      region: foobar
                      interface: public
                      url: 'https://foo.bar.cloud:443/v1/AUTH_CUSTOM_ID'

[haphan]

The python implementation allows overrides to happen at the Swift client level.

What do you think if we can learn from that pattern to avoid coupling Identity service with the S3 client?

[drzraf]

I'm sorry, which coupling are you referring to?

In this PR the endpoint URL override has been made very generic (probably much much more than what need in real-world scenario that would mostly apply to swift and cross-project application credentials or, at best, cross-project ACL).

It's good because, well, it's generic (and, as such, does not touch swift-specifics or tight together different level of components) but may be seen as less obvious to configure than the straight OS_STORAGE_URL environment variable that Python swiftclient supports.

[drzraf]

Dears, I would be happy to see this in.

[k0ka]

Hello,

Can you add some documentation and tests for this feature?

[drzraf]

Sadly not. I'm not currently working on this and can't find the time to dig into it again.

[drzraf]

@k0ka : Doc:

Generally, resources and credentials match are expected to match (same project id). But in some cases user credentials may grant access to a container from another project (different OS_STORAGE_URL) the user originates from.
In order to bypass the usual automatic URL/resource derivation logic, catalog_overrides can be used to specify an alternative url that will apply as a replacement for a given service.
The service to match is specified by either at least its name or its type (or both) and optional additional restrictions can be added based on the region and/or the interface.

For example:

                catalog_overrides:
                    - name: swift
                      type: object-store
                      region: abc
                      interface: public
                      url:  https://abc.com/v1/AUTH_123456

will override the OS_STORAGE_URL with url when requesting the public object-store service called swift located in abc. This is necessary if the user wasn't created within the project 123456