feat: make force_destroy configurable

[ferrarimarco]

Description

Use a variable to set the force_destroy attribute of the Cloud Storage bucket to store the Terraform state. This is helpful to simplify the related tutorial because we can ask users to adjust the value of the variable, instead of asking them to modify the source code.

Checklist

Readiness

• [x] Yes, merge this PR after it is approved
• [ ] No, don't merge this PR after it is approved

Style

• [x] My sample follows the rules described for Terraform in the Effective Samples style guide
• [x] My sample follows the other requirements and best practices in the Contributing guide

Testing

• [x] I have performed tests described in the Contributing guide:

  • [x] Tests pass: terraform apply
  • [x] Lint pass: terraform fmt check

Intended location

• [x] Yes, this sample will be (or already is) included on cloud.google.com Location(s):

• [ ] No, this sample won't be included on cloud.google.com Reason:

API enablement

• [ ] If the sample needs an API enabled to pass testing, I have added the service to the Test setup file

Review

• [ ] If this sample adds a new directory, I have added codeowners to the CODEOWNERS file

[ferrarimarco]

/cc @nityaravi

[bharathkkb]

@ferrarimarco @glasnt For samples it would be better to ask user to modify inline rather than exposing a var. https://googlecloudplatform.github.io/samples-style-guide/#no-global-variables

[glasnt]

Good point, @bharathkkb. I was working with the description from the PR as to why this was being included.

@ferrarimarco If you could share your usage with me, including your intended tutorial updates, we can adjust to adhere to the styleguide (glasnt@)