Instance cache

[krystian-panek-vmltech]

fixes #350, #349

[Copilot]

Pull request overview

This PR introduces an in-memory, per-Instance cache to avoid repeated HTTP requests for status-derived values that are effectively constant while an AEM instance is running (notably system properties and derived values like timezone), addressing the /system/console/status-System%20Properties.json request storm described in #349/#350.

Changes:

• Added InstanceCache with a config flag (instance.cache.enabled, default true) and unit tests, plus template YAML updates to expose the setting.
• Updated Status methods to use InstanceCacheGet for SystemProps, SlingProps, SlingSettings, and AemVersion (while avoiding caching the “unknown during startup” case).
• Reduced per-event timezone resolution cost in EventStableChecker and ensured cache invalidation on local instance start/stop.

Reviewed changes

Copilot reviewed 13 out of 13 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
pkg/status.go	Uses InstanceCacheGet to cache status-derived values and fixes TimeLocation() error propagation.
pkg/instance_cache.go	Introduces the per-instance in-memory cache and generic cached-loader helper.
pkg/instance_cache_test.go	Adds unit tests validating caching, non-caching of errors, clearing, and concurrent access.
pkg/instance.go	Adds cache *InstanceCache to Instance and exposes it via Cache().
pkg/instance_manager.go	Initializes the instance cache during instance construction.
pkg/local_instance.go	Clears the instance cache after local start/stop to avoid stale cached values across lifecycle changes.
pkg/check.go	Avoids per-event timezone resolution by reusing the location from instance.Now().
pkg/cfg/defaults.go	Defaults instance.cache.enabled to true.
aem/default/etc/aem.yml	Documents/enables instance cache in the default project template config.
examples/docker/src/aem/default/etc/aem.yml	Documents/enables instance cache in the docker example template config.
pkg/project/instance/aem/default/etc/aem.yml	Documents/enables instance cache in the instance project template config.
pkg/project/app_cloud/aem/default/etc/aem.yml	Documents/enables instance cache in the app_cloud template config.
pkg/project/app_classic/aem/default/etc/aem.yml	Documents/enables instance cache in the app_classic template config.

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