Change network isolation policy from Permissive to Preferred in 1ES pipeline template

[Copilot]

Changes networkIsolationPolicy from Permissive to Preferred in the 1ES pipeline template to use a more secure network isolation policy while still allowing access to common public services.

Changes

• Changed networkIsolationPolicy: Permissive to networkIsolationPolicy: Preferred in eng/pipelines/templates/stages/1es-redirect.yml
• Retained the associated comment referencing the 1ES network isolation documentation

Impact

Pipelines will now use the Preferred network isolation policy, which provides a balanced approach between security and functionality. This policy allows access to common public services (GitHub, NuGet, Maven Central, etc.) while maintaining better security than the Permissive policy.

The Preferred policy is the recommended setting for common use cases and should not cause breaking changes for typical pipeline jobs that use standard public services.

Original prompt

Create a draft pull request in Azure/azure-sdk-for-java that removes the networkIsolationPolicy: Permissive setting from eng/pipelines/templates/stages/1es-redirect.yml.

Requirements

• Edit only what is necessary to remove networkIsolationPolicy: Permissive from the YAML.
• Ensure the YAML remains valid and pipeline behavior is otherwise unchanged.
• If there are related references or comments explaining the setting, update them accordingly.

Validation

• Confirm the pipeline template YAML passes basic YAML validation.
• If the repository has a pipeline/template linting step or validation command documented, run it and include results in the PR description.

Notes

• Make the PR a draft.
• Include a clear PR title and description explaining why the permissive network isolation policy is being removed and any potential impact.

This pull request was created from Copilot chat.

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[raych1]

@copilot change it to "networkIsolationPolicy: Preferred"

[Copilot]

Changed to networkIsolationPolicy: Preferred in commit 53b492d.