Remove TLS subscriptions that 404 from state

[bendrucker]

When a TLS subscription is removed outside of Terraform, currently it causes refreshes to fail

╷
│ Error: 404 - Not Found:
│ 
│     Title:  Not found
│     Detail: The subscription you requested was not found

Instead, the provider should remove these resources from state. This is handled in other resources but the exact implementation differs a bit by resource.

[smaeda-ks]

Hi @bendrucker, thanks for the PR.

tls_subscription_validation is a virtual resource so I don't think it's worth adding this logic in there. Could you please undo that?

[bendrucker]

Hey @smaeda-ks I thought it might still help address the following scenario:

1. I apply configuration that creates a tls_subscription and uses the validation resource to wait for completion
2. I delete the TLS subscription outside of Terraform
3. I re-apply the configuration

The result should be the same after steps 1 and 3. Without this logic in the validation resource, I expect the same error would occur on refresh during step 3, requiring state rm to proceed.

[smaeda-ks]

ok, thanks. I'll give it a try and get back to you.

[smaeda-ks]

Added a commit to change the way to return the warning message (and removed nesting).