feat: use dynamic dns resolution for upstreams in oss like plus

[dekobon]

Proposed changes

This change unifies the OSS upstream configuration with the Plus upstream configuration, so that both are using dynamic DNS reconfiguration for upstreams.

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[Copilot]

Pull Request Overview

This PR unifies the upstream configuration for OSS and Plus by switching both to dynamic DNS reconfiguration, ensuring consistent behavior across both editions.

• Updated the comment in the Plus configuration file to remove specific NGINX Plus references.
• Modified the OSS configuration file to add a dynamic DNS resolution directive with an upstream zone and a "resolve" modifier.

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
plus/etc/nginx/templates/upstreams.conf.template	Removed explicit mention of NGINX Plus in favor of unified config.
oss/etc/nginx/templates/upstreams.conf.template	Added an upstream zone directive and the "resolve" parameter to enable dynamic DNS reloading.

Comments suppressed due to low confidence (1)

plus/etc/nginx/templates/upstreams.conf.template:1

• [nitpick] The removal of 'NGINX Plus' from the comment is intended to unify the configurations; please ensure that any documentation referring to Plus still clarifies the differences, if any, between the OSS and Plus deployments.

# This configuration should dynamically reload S3 backends

[dekobon]

recheck