Dynamic IdP configuration after container starts

[neerolyte]

In my environment it's impractical to predict the path the SP remote ends up on until after we already need to have started the IdP container, we also use a different SP remote for each test case. I would also like the ability to configure users and their metadata from within tests so that it's trivial to see the important bits of the environment set up for the test and the test assertions in a single spot. I also create unique usernames in tests currently so that when a test is being run locally we can keep adding users from the same test without having username collisions in our app.

While this is all likely achievable using volume mounts over the config files shared between multiple containers, that requires our test containers knowing about the file system layout in the IdP container and assuming that that will never change.

I'd like a simple API deployed in the IdP container to make changes via basic POST requests for at least adding:

• a new SP remote
• a new user and metadata to the example-userpass auth source

I've started mocking that out in master...neerolyte:dynamic-test-config and I'd like feedback on whether you'd merge something like this if you have a chance.