Add hydration support for Content::CONTENT_TYPE_ATTACHMENT

[virtualLast]

The content API exposes attachment children through:

$contentApi->children(
    $page,
    Content::CONTENT_TYPE_ATTACHMENT,
);

This calls the expected Confluence REST endpoint:

GET /content/{pageId}/child/attachment

However, attachment results cannot currently be hydrated.

The response is passed through ContentSearchResult::load(), which delegates each result to AbstractContent::load(). That method only maps the page and comment content types, so attachment results throw:

HydrationException: Invalid content type: attachment

The library already defines:

Content::CONTENT_TYPE_ATTACHMENT

so this appears to be incomplete attachment support rather than an unsupported endpoint.

My proposed scope would be:

• add a ContentAttachment entity extending AbstractContent
• map Content::CONTENT_TYPE_ATTACHMENT in AbstractContent::load()
• hydrate common content fields
• hydrate stable attachment-specific fields where available, such as media type, file size and download link
• add tests covering direct attachment hydration and attachments returned through ContentSearchResult

I would keep attachment uploading, replacement and binary downloading outside the scope of the initial change.

Happy to discuss and amend as you see fit