This commit renames all secure_media related settings to secure_uploads_* along with the associated functionality.
This is being done because "media" does not really cover it, we aren't just doing this for images and videos etc. but for all uploads in the site.
Additionally, in future we want to secure more types of uploads, and enable a kind of "mixed mode" where some uploads are secure and some are not, so keeping media in the name is just confusing.
This also keeps compatibility with the `secure-media-uploads` path, and changes new
secure URLs to be `secure-uploads`.
Deprecated settings:
* secure_media -> secure_uploads
* secure_media_allow_embed_images_in_emails -> secure_uploads_allow_embed_images_in_emails
* secure_media_max_email_embed_image_size_kb -> secure_uploads_max_email_embed_image_size_kb
This commit introduces a new site setting: `block_hotlinked_media`. When enabled, all attempts to hotlink media (images, videos, and audio) will fail, and be replaced with a linked placeholder. Exceptions to the rule can be added via `block_hotlinked_media_exceptions`.
`download_remote_image_to_local` can be used alongside this feature. In that case, hotlinked images will be blocked immediately when the post is created, but will then be replaced with the downloaded version a few seconds later.
This implementation is purely server-side, and does not impact the composer preview.
Technically, there are two stages to this feature:
1. `PrettyText.sanitize_hotlinked_media` is called during `PrettyText.cook`, and whenever new images are introduced by Onebox. It will iterate over all src/srcset attributes in the post HTML and check if they're allowed. If not, the attributes will be removed and replaced with a `data-blocked-hotlinked-src(set)` attribute
2. In the `CookedPostProcessor`, we iterate over all `data-blocked-hotlinked-src(set)` attributes and check whether we have a downloaded version of the media. If yes, we update the src to use the downloaded version. If not, the entire media element is replaced with a placeholder. The placeholder is labelled 'external media', and is a link to the offsite media.
Previously this mapping of **cooked** images was only being run for oneboxes. Now it runs for all images, so we can transform hotlinked images without needing to immediately update `raw`
PostAnalyzer and CookedPostProcessor both replace URLs with oneboxes.
PostAnalyzer did not use the max_oneboxes_per_post site and setting and
CookedPostProcessor replaced at most max_oneboxes_per_post URLs ignoring
the oneboxes that were replaced already by PostAnalyzer.
```
warning: Passing a Node as the second parameter to Node.new is deprecated. Please pass a Document instead, or prefer an alternative constructor like Node#add_child. This will become an error in a future release of Nokogiri.
```
