Move GCP projece attribute onto resources, inherit from provider

[sethvargo]

This commit uses the existing pattern in the provider for "region", but extends it to "project" as well. Currently the provider is heavily tied to a project. Some of the upcoming APIs (that we would like to leverage) do not require a project id. This PR decouples the provider configuration from the project configuration, but does so in a backwards-compatible way.

Highlight changes:

• provider/google.project: required => optional
• resource/google_*: +project attribute (with some exceptions)
• Updated all docs with the new resource

/cc @lwander @jen20

[sethvargo]

One important thing to note here is the plan vs. apply validation. Because the provider is not configured during validateWalk, a config like this will have a successful plan phase even though no value was provided for "project" in the provider configuration:

provider "google" {
  credentials = "${file("creds.json")}"
}

resource "google_compute_network" "default" {
  name       = "test"
  ipv4_range = "10.0.0.0/16"
}

This is because, due to the way providers are loaded, we don't have the provider data until we start running the function. As such, the apply will quickly error out, before actually making any API calls for the resource, when trying to read the value and finding it's nil.

I think this is "ok" until we can refactor Terraform's core to load provider configs in validateWalk, and I saw this pattern already exists in a few other places in Terraform. In reality, the probability for that type of error is quite minimal, and the gained-tradeoff is that we can now manage multiple projects in a single Terraform config 😄

[lwander]

Thanks for moving these in in here, resource_compute_address.go definitely wasn't the place for getRegion.

[lwander]

Hey just to make sure I didn't miss anything: You'll be adding the project resource in a separate PR? Also, you mention that some resources weren't updated with the new project attribute - which ones didn't need it?

Otherwise, LGTM! Thanks for updating the docs too.

[sethvargo]

Hey @lwander

Yup! This PR was already rather large, so I didn't want to add any new resources yet. I'm going to do that in another PR once this lands in core 😄

[sethvargo]

@lwander whoops, missed the second part of your Q:

All the storage_bucket_* resources don't have a project attribute.

[ghost]

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