feat: Add log export GCS bucket object versioning

[vovinacci]

As per original issue, the storage bucket created by the storage_destination module does not have object versioning enabled, which is generating a finding in SHA against the CIS Benchmark for GCP. This PR:

• Updates underlying log-export module version to 5.1.0 as GCS object versioning is supported starting this version.
• Adds a note on GCS object versioning in general README.

Closes #274

[vovinacci]

@rjerrems @bharathkkb Integration tests failed, checked the test spec - didn't find anything that may have been broken by this PR. As I don't have access to cloud build for this project, could you please take a look on what it failed? Much appreciated.

[rjerrems]

Thanks for this @vovinacci ! I think we may need to merge this PR first, as a number of changes have been made to how tests are run to accommodate it #298 (which are likely breaking your build)

[vovinacci]

@rjerrems Thanks much for the heads-up. I've tested this change against master in our repository and it was just fine. Should be reasonably safe to merge. Thanks!

P.S. Alternatively, I can target it to master and then backport to develop after #298 is merged.

Edit: Please disregard this comment, I've completely misread written above.

[bharathkkb]

Thanks for the PR @vovinacci
LGTM, we can rebase this on dev once #298 merged, which should fix the tests.

[vovinacci]

@bharathkkb Rebased, tests still failing. Could you please take a look? Many thanks in advance.

[rjerrems]

It looks like both are failing on shared with

       Error: Invalid value for input variable
       
       The environment variable TF_VAR_policy_id does not contain a valid value for
       variable "policy_id": a number is required.

[vovinacci]

export TF_VAR_policy_id=$(gcloud access-context-manager policies list --organization="${TF_VAR_org_id:?}" --format="value(name)") is used quite a lot in terraform modules (build/int.cloudbuild.yaml). Tried this command locally, very rare after the expected number output it asks if user want to provide a feedback. May this be an issue? I didn't have a chance to look at the source to determine the frequency/randomness of this event, but will do it later on this week.

[bharathkkb]

/gcbrun

[bharathkkb]

@vovinacci one of the other CFT module tests removes the access-context-manager policy during teardown and that caused an issue. I have restarted the tests.

[vovinacci]

@bharathkkb Looks good now!

P.S. Are there any plans to make cloudbuild test output available for everyone to view? I do miss it really. :)

[bharathkkb]

@vovinacci we recently added the ability for contributors to get feedback from the cloudbuild lint tests (should now be enabled for this repo), but not for the integration tests. I'll add this to our backlog.