GKEhubFeatureMembership's spec.membershipLocation field should be optional and discouraged to use

[ziyue-101]

Checklist

• I did not find a related open issue.
• I did not find a solution in the troubleshooting guide: (https://cloud.google.com/config-connector/docs/troubleshooting)
• If this issue is time-sensitive, I have submitted a corresponding issue with GCP support.

Bug Description

The spec.memebrshipLocation field defaults to global if not set. The field would be required if the corresponding memebreship is regional. This is because the spec.memebrshipLocation field needs to match exactly the same as the corresponding Membership resource's spec.location field. However, the featuremembership resource already has the membershipRef, it should be able to infer the memebership location value from the referenced resource.

The redundant field confuses users and would cause problems if two location values are set differently in two places.

I would consider this as a design flaw in the current controller backed by DCL.
In the future direct controller, we should get the membershipLocation value from the referenced resource instead of depending on the field.

Additional Diagnostic Information

n/a

Kubernetes Cluster Version

n/a

Config Connector Version

n/a

Config Connector Mode

namespaced mode (default)

Log Output

No response

Steps to reproduce the issue

• Create a GKEHubMembership resource in us-central1
• Create a Gkehubfeaturemembership resource with spec.membershipLocation as empty
• The Gkehubfeaturemembership KCC resource will fail to create the GCP resource

YAML snippets

No response