adding data source for identity pool

[wvanderdeijl]

follow up to PR #4071 and part of bigger issue hashicorp/terraform-provider-google#7455

If this PR is for Terraform, I acknowledge that I have:

• Searched through the issue tracker for an open issue that this either resolves or contributes to, commented on it to claim it, and written "fixes {url}" or "part of {url}" in this PR description. If there were no relevant open issues, I opened one and commented that I would like to work on it (not necessary for very small changes).
• Generated Terraform, and ran make test and make lint to ensure it passes unit and linter tests.
• Ensured that all new fields I added that can be set by a user appear in at least one example (for generated resources) or third_party test (for handwritten resources or update tests).
• Ran relevant acceptance tests (If the acceptance tests do not yet pass or you are unable to run them, please let your reviewer know).
• Read the Release Notes Guide before writing my release note below.

Release Note Template for Downstream PRs (will be copied)

`google_iam_workload_identity_pool`

[modular-magician]

Hello! I am a robot who works on Magic Modules PRs.

I have detected that you are a community contributor, so your PR will be assigned to someone with a commit-bit on this repo for initial review.

Thanks for your contribution! A human will be with you soon.

@danawillow, please review this PR or find an appropriate assignee.

[wvanderdeijl]

Unfortunately when I run the test it fails:

2020/10/21 15:01:21 [DEBUG] Retry Transport: Returning after 1 attempts
    TestAccDataSourceIAMBetaWorkloadIdentityPool_basic: testing_new_config.go:88: no "id" found in attributes
    TestAccDataSourceIAMBetaWorkloadIdentityPool_basic: testing_new.go:57: no "id" found in attributes
--- FAIL: TestAccDataSourceIAMBetaWorkloadIdentityPool_basic (18.68s)
FAIL
FAIL	github.com/hashicorp/terraform-provider-google-beta/google-beta	19.425s
FAIL
make: *** [testacc] Error 1

when enabling TF logging it seems like the datasource is trying to do a GET before the resource is created. I guess the workload_identity_pool_id attribute from the resource is already know before creating the actual resource, so the datasource thinks it has enough information to do the GET.
Does anybody know how to fix this?

[modular-magician]

Hi! I'm the modular magician. Your PR generated some diffs in downstreams - here they are.

Diff report:

Terraform GA: Diff ( 4 files changed, 47 insertions(+))
Terraform Beta: Diff ( 5 files changed, 113 insertions(+))

[modular-magician]

Hi! I'm the modular magician. Your PR generated some diffs in downstreams - here they are.

Diff report:

Terraform GA: Diff ( 4 files changed, 47 insertions(+))
Terraform Beta: Diff ( 5 files changed, 121 insertions(+))

[danawillow]

/gcbrun

[modular-magician]

I have triggered VCR tests based on this PR's diffs. See the results here: "https://ci-oss.hashicorp.engineering/viewQueued.html?itemId=153647"

[modular-magician]

Hi! I'm the modular magician. Your PR generated some diffs in downstreams - here they are.

Diff report:

Terraform GA: Diff ( 4 files changed, 47 insertions(+))
Terraform Beta: Diff ( 5 files changed, 121 insertions(+))

[modular-magician]

I have triggered VCR tests in RECORDING mode for the following tests that failed during VCR: TestAccDataSourceIAMBetaWorkloadIdentityPool_basic|TestAccDataSourceSpannerInstance_basic You can view the result here: "https://ci-oss.hashicorp.engineering/viewQueued.html?itemId=153652"

[wvanderdeijl]

@danawillow do you want me to make more changes to this PR, or is this good to go?
I still don't understand why the datasource tests fail at my end, but we can ignore that if the tests succeed at your end.
Also, if you want me to change the workload_identity_pool_id behaviour I would need some guidance on how to do that as I feel I have followed the example given to met in #4071

[danawillow]

@slevenick can you take this over from me?

[slevenick]

/gcbrun

[modular-magician]

I have triggered VCR tests based on this PR's diffs. See the results here: "https://ci-oss.hashicorp.engineering/viewQueued.html?itemId=154827"

[modular-magician]

Hi! I'm the modular magician. Your PR generated some diffs in downstreams - here they are.

Diff report:

Terraform GA: Diff ( 4 files changed, 47 insertions(+))
Terraform Beta: Diff ( 5 files changed, 121 insertions(+))

[modular-magician]

I have triggered VCR tests based on this PR's diffs. See the results here: "https://ci-oss.hashicorp.engineering/viewQueued.html?itemId=155055"

[modular-magician]

I have triggered VCR tests in RECORDING mode for the following tests that failed during VCR: TestAccDataSourceSpannerInstance_basic|TestAccBigqueryDataTransferConfig|TestAccMonitoringSlo_monitoringSloRequestBasedExample You can view the result here: "https://ci-oss.hashicorp.engineering/viewQueued.html?itemId=155141"

[slevenick]

Tests pass, seems fine to me. Just request the beta-only note in the docs

[slevenick]

We probably want a note that this resource is in beta only here:

~> **Warning:** This resource is in beta, and should be used with the terraform-provider-google-beta provider.
See [Provider Versions](https://terraform.io/docs/providers/google/guides/provider_versions.html) for more details on beta resources.

is the one that we generally use

Similar to: https://registry.terraform.io/providers/hashicorp/google/latest/docs/resources/compute_managed_ssl_certificate

[wvanderdeijl]

Done

[modular-magician]

Hi! I'm the modular magician. Your PR generated some diffs in downstreams - here they are.

Diff report:

Terraform GA: Diff ( 4 files changed, 50 insertions(+))
Terraform Beta: Diff ( 5 files changed, 124 insertions(+))

[slevenick]

Thanks!

[slevenick]

Huh, I can't merge as Dana's review requested changes. @danawillow can you remove yourself from this PR, I can't seem to do it