adds basic checking of subscription state

[s-amann]

What this PR does

Before this PR:
Subscription state was not validated when making requests belonging to a subscription

After this PR:
Subscription state is validated, meaning, requests must be using a subscriptionID which has a 'registered' state stored in the frontends cache.

To add any subscription as registered to the frontend cache run

curl -X PUT localhost:8443/subscriptions/SUBSCRIPTION_ID?api-version=2.0 -H 'content-type: application/json' -d '{"state":"Registered"}'

Jira: ARO-6313
Link to demo recording:

Special notes for your reviewer

Checklist

This checklist is not enforcing, but it's a reminder of items that could be relevant to every PR.
Approvers are expected to review this list.

• PR: The PR description is expressive enough and will help future contributors
• Code: Write code that humans can understand and Keep it simple
• Refactor: You have left the code cleaner than you found it (Boy Scout Rule)
• Upgrade: Impact of this change on upgrade flows was considered and addressed if required
• Deployment: The deployment process was considered and addressed if required
• Testing: New code requires new unit tests.
• Documentation: Is the documentation updated? Either in the doc located in focus area, in the README or in the code itself.
• Customers: Is this change affecting customers? Is the release plan considered?

[AldoFusterTurpin]

I know it is in draft mode, but just two minor suggestions in case they make sense to you. Thanks! 🙂

[mbarnes]

Had a suggestion that would require a bit of refactoring, so I'll leave it up to you. LGTM otherwise.

[bennerv]

can we get jira link in PR?

[mbarnes]

Couple questions about API versions and the subscription endpoint:

• Can we remove /internal/api/subscription/register.go?
  I was going to suggest using a different middleware chain for this endpoint that omits MiddlewareValidateAPIVersion (since that's only meant for our API versions) but it looks like you've effectively done that already.

• Should ArmSubscriptionAction be verfiying the api-version parameter is "2.0"?

[s-amann]

Couple questions about API versions and the subscription endpoint:

• Can we remove /internal/api/subscription/register.go?
  I was going to suggest using a different middleware chain for this endpoint that omits MiddlewareValidateAPIVersion (since that's only meant for our API versions) but it looks like you've effectively done that already.

I can delete subscription/register.go - I only needed this before removing the endpoint from our api version validation.

• Should ArmSubscriptionAction be verfiying the api-version parameter is "2.0"?

I'm not sure about this, the docs say "system version 2.0" will be used, but it doesn't say anything about requiring 2.0

[mbarnes]

LGTM. 👍 on moving subscription structs into the arm package.