fix(appstore): honor subclass cache invalidation duration in fetchers

[joshtrichards]

• Resolves: #

Summary

AppDiscoverFetcher declares:

public const INVALIDATE_AFTER_SECONDS = 86400;

However, the base class (Fetcher) uses self::INVALIDATE_AFTER_SECONDS, causing AppDiscoverFetcher's override value to be ignored.

Therefore the discover fetcher does not actually use 24 hours through this mechanism; it still uses the base class’s one-hour/15-minute thresholds.

Changes:

• Use late static binding when resolving INVALIDATE_AFTER_SECONDS.

Allows AppDiscoverFetcher to use its existing 24-hour cache duration override as (presumably) intended. Preserves the existing default duration for fetchers that do not override the constant.

TODO

• Backport

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• Tests (unit, integration, api and/or acceptance) are included
• Screenshots before/after for front-end changes
• Documentation (manuals or wiki) has been updated or is not required
• Backports requested where applicable (ex: critical bugfixes)
• Labels added where applicable (ex: bug/enhancement, 3. to review, feature component)
• Milestone added for target branch/version (ex: 32.x for stable32)

AI (if applicable)

• The content of this PR was partly or fully generated using AI

[joshtrichards]

/backport to stable34

[joshtrichards]

/backport to stable33

[joshtrichards]

/backport to stable32

[CarlSchwan]

Good catch