Add AppScope Configuration

[hongchaodeng]

As proposed in https://github.com/microsoft/hydra-spec/issues/144, this tries to define app-scope config and decouple it from AppConfig.

I have done writing the spec, but haven't decided where to put it in the page order.

[hongchaodeng]

cc @mikkelhegn

[wonderflow]

can you add an example of HealthScope

[hongchaodeng]

Sure thing.
I am still waiting for more feedback from @mikkelhegn @technosophos @suhuruli to see if we all agree on this spec/model.
Once consensus is made, I will add more examples to demonstrate usability!

[technosophos]

A request came in that we re-do the organization of the application model so that there is an explicit ApplicationModel type that can define an entire app. It is entirely a work in progress, but I threw something together in #148 so that I can show it later this week to the various parties who requested it.

Do you think we could combine this and the app model into one thing?

[hongchaodeng]

Do you think we could combine this and the app model into one thing?

I do not think app model will solve this problem.
https://github.com/microsoft/hydra-spec/pull/148 looks absolutely promising. It solves the schema problems.

https://github.com/microsoft/hydra-spec/issues/144 and this PR is trying to solve the deployment problem.
Once https://github.com/microsoft/hydra-spec/pull/98 is merged, we will also need to update the AppConfig part to use this app-scope config.

[mikkelhegn]

LGTM - did not check consistency with recent changes though... :-)

[hongchaodeng]

@mikkelhegn

After discussion with Matt and Sudhanva, we have agreed to not add new concept but reuse existing AppConfig. The idea is that AppConfig will define global scopes to solve such cases. I'm pulling up new PRs to make it well-written in the docs and fix the definitions as well.

Thanks again for looking after it! Will ping once change is pulled up.