Cache base image metadata to speed up GetBase

[jonathan-conder]

Description

The slow part of GetBase is downloading a big JSON file with all the images inside. LXD has a builtin mechanism to cache this download for 1 hour. We just need to give it a place to store the data.

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[Copilot]

Pull Request Overview

This PR improves performance of the GetBase operation by implementing caching for base image metadata downloads. The LXD library already supports caching downloaded JSON metadata for 1 hour; this PR enables that feature by providing a cache directory path.

Key changes:

• Introduces a new BaseDownloads cache directory for storing base image metadata
• Passes the cache path to the LXD SimpleStreams connection
• Fixes the image type parameter in GetImageAliasType to use the correct source field

Reviewed Changes

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

File	Description
internal/dirs/dirs.go	Adds BaseDownloads directory variable and ensures it's created during initialization
internal/workshop/lxd/lxd_base_manager.go	Enables metadata caching by passing cache path to SimpleStreams connection and fixes image type parameter

[github-actions]

TICS Quality Gate

✔️ Passed

workshop

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The following files have been checked for this project

• internal/dirs/dirs.go
• internal/workshop/lxd/lxd_base_manager.go

Automatic-tests / code-coverage / TICS GitHub Action