Enable shared yum cache for mock builds

[andrewlukoshko]

Summary

Add support for sharing the yum/dnf package cache across mock builds of the same platform and architecture. This avoids redundant package downloads when multiple builds run for the same platform/arch combination, improving build performance.

Changes

Shared yum cache (use_shared_yum_cache)

When use_shared_yum_cache: true is set in a platform's data.mock config, the build node generates a cache_key in mock.cfg based on the platform name and target architecture:

config_opts["plugin_conf"]["yum_cache_opts"]["cache_key"] = "almalinux-kitten-10-x86_64"

This tells mock's yum_cache plugin to share the cached packages across all builds matching that key, instead of maintaining separate caches per chroot.

Yum caching options (keepcache, metadata_expire)

Platform configs can now set keepcache and metadata_expire in data.yum to control yum.conf caching behavior inside the chroot. AlmaLinux-Kitten-10 is configured with keepcache: true and metadata_expire: 60.

Nested dict support in MockConfig

MockConfig.render_config_option now supports two-level nested dictionaries, enabling direct setting of plugin_conf options without resetting existing plugin defaults.

Pull Requests

• Add shared_cache_key to MockConfig and keepcache/metadata_expire to YumConfig albs-build-lib#5 — nested dict support in render_config_option, keepcache and metadata_expire parameters in YumConfig
• Pass shared_cache_key to MockConfig for shared yum cache builds albs-node#221 — shared yum cache handling in build node
• Enable shared yum cache and caching options for AlmaLinux-Kitten-10 albs-web-server#1210 — enable use_shared_yum_cache, keepcache, and metadata_expire for AlmaLinux-Kitten-10

Merge order: albs-build-lib → albs-node → albs-web-server

[andrewlukoshko]

Updated the implementation based on review feedback to leverage MockConfig directly instead of manually assembling nested plugin_conf dicts from albs-node.

What changed

shared_cache_key is now a first-class MockConfig parameter (albs-build-lib). Instead of having albs-node build nested dicts and call set_config_opts({'plugin_conf': {'yum_cache_opts': {'cache_key': ...}}}), MockConfig accepts shared_cache_key and renders the plugin_conf line directly in dump_to_file(). This keeps mock caching logic centralized in albs-build-lib alongside the existing MockSupervisor cache management.

Nested dict support in render_config_option was reverted — no longer needed since shared_cache_key is handled natively.

albs-node is simplified to just:

shared_cache_key = '{}-{}'.format(task.platform.name.lower(), target_arch)
mock_config = MockConfig(..., shared_cache_key=shared_cache_key, ...)

PRs (updated)

• Add shared_cache_key to MockConfig and keepcache/metadata_expire to YumConfig albs-build-lib#5 — shared_cache_key parameter in MockConfig, keepcache/metadata_expire in YumConfig
• Pass shared_cache_key to MockConfig for shared yum cache builds albs-node#221 — pass shared_cache_key to MockConfig constructor
• Enable shared yum cache and caching options for AlmaLinux-Kitten-10 albs-web-server#1210 — enable use_shared_yum_cache, keepcache, metadata_expire for AlmaLinux-Kitten-10