[bug] fix fastly_tls_subscription resource to properly handle challenges for multi-SAN

[smaeda-ks]

fix for: #430

Looks like when this resource was originally implemented, multi-SAN cert subscription wasn't taken into account. Specifically, this part...
https://github.com/fastly/terraform-provider-fastly/blob/v0.32.0/fastly/resource_fastly_tls_subscription.go#L176

Therefore, the state file only includes the first domain's challenge data, which is a bug.

Though this is definitely going to be a breaking change.

[Integralist]

This looks OK to me, but we don't want to merge this until we've discussed a major 1.0.0 release (@smaeda-ks I'll be having discussions with @bengesoff about 1.0.0 as part of our Q3 goals).

In the mean time I'd also want to get @bengesoff's approval of these changes too.

[bengesoff]

Think make generate-docs needs rerunning, but otherwise LGTM 👍🏼

[smaeda-ks]

pushed doc update

[virgofx]

Any chance to get this merged and a release cut? Our workaround is to create separate subscriptions per domain :(

[Integralist]

Hi @virgofx the current implementation is considered a breaking change and so would need to be part of a 1.0.0 release (something we're actively working towards at the moment, but unfortunately I couldn't say with certainty as to when exactly it would be ready to release).

In the meantime I'm discussing with the team potential workarounds that don't result in a breaking change.

[smaeda-ks]

Please merge this. Thanks

[virgofx]

Thanks for merging! Can you please cut the 1.0.0 release so consumers can make use of this great work 😃

[Integralist]

Hi @virgofx this change will actually go into a 0.33.0 release. We're actively fixing some broken integration tests at the moment, but once we have those fixed I'll be cutting that new release 🙂