Fix post cache

[leogermani]

Description of the Change

Fixes a typo in DistributorPost::parse_media_blocks that was not correctly parsing the post ID into the cache key.

This was causing the cache for all posts to be stored into the same key and override the cache from a previous cached post.

In environments that use persistent cache, this would cause distributed images to send the wrong images out sites.

How to test the Change

This will most likely only affect environments using persistent cache. But by adding some debugging before and after this change you can confirm that the cache is not being saved with the correct key, in which the post ID is parsed.

Changelog Entry

Fixed - Caching Post images

Credits

Props @leogermani

Checklist:

• [x] I agree to follow this project's Code of Conduct.
• [ ] I have updated the documentation accordingly.
• [x] I have added tests to cover my change.
• [x] All new and existing tests pass.

[leogermani]

Thanks for catching this @leogermani.

This looks good to me and tests well.

@peterwilsoncc Thank you.

This creates a huge mess when using persistent cache in the network of sites. We are being able to workaround it by clearing this cache entry on every request, but it would be great to have this released as soon as you think it's convenient.

Thanks again.