Add immutable property to Gateway resource fields

[JamesDuncanNz]

Description

Mark name and location parameters as immutable: true on Gateway.

Previously, immutable: true was missing on the URL parameters name and location in mmv1/products/networkservices/Gateway.yaml. As a result, the generated Terraform schema did not have ForceNew: true, causing Terraform to erroneously plan an in-place update when either field was changed. During apply, this resulted in an invalid PATCH request to the new resource name/location endpoint and failed on subsequent state read with:

Error: Provider produced inconsistent result after apply
Root object was present, but now absent.

Adding immutable: true ensures Terraform correctly plans a destroy-and-recreate (ForceNew) when name or location is changed.

Release Note Template for Downstream PRs (will be copied)

networkservices: fixed `google_network_services_gateway` to force replacement (`ForceNew`) when `name` or `location` is modified

[github-actions]

Googlers: For automatic test runs see go/terraform-auto-test-runs.

@SirGitsalot, a repository maintainer, has been assigned to review your changes. If you have not received review feedback within 2 business days, please leave a comment on this PR asking them to take a look.

You can help make sure that review is quick by doing a self-review and by running impacted tests locally.

[modular-magician]

Hi there, I'm the Modular magician. I've detected the following information about your changes for commit 6751f35:

Diff report

Your PR generated the following diffs in downstream repositories:

Repository	Diff Link	Changes
google provider	View Diff	1 file changed, 2 insertions(+)
google-beta provider	View Diff	1 file changed, 2 insertions(+)
terraform-google-conversion	View Diff	1 file changed, 2 insertions(+)

Test report

Analytics

Total Tests	Passed	Skipped	Affected
102	100	2	0

Affected Service Packages

• networkservices

Learn how VCR tests work

---

Step 1: Replaying Mode

🟢 All tests passed in Replaying mode! No Recording was needed.

View the replaying VCR build log

@JamesDuncanNz, @SirGitsalot VCR tests complete for 6751f35!

[SirGitsalot]

Fixes hashicorp/terraform-provider-google#27894