### Background
Several call sites use `FileStore#download` (through `Discourse.store.download`). In some cases the author seems aware that the method can raise an error if the download fails, and in some cases not. Because of this we're seeing some of these exceptions bubble all the way up and getting logged in production. Although they are not really actionable at that point. Rather each call site needs to be considered to figure out how to handle them.
### What is this change?
This change accomplishes primarily two things.
Firstly it separates the method into a safe version which will handle errors by returning `nil`, and an unsafe version which will re-package upstream errors in a new `FileStore::DownloadError` class.
Secondly it updates the call sites which have been doing error handling downstream to use the new safe version.
For backwards compatibility, there's an interim situation and a desired end state.
**Interim:**
```
FileStore#download → Old unsafe version. Will raise any error and show a deprecation warning.
FileStore#download! → New unsafe version. Will raise FileStore::DownloadError.
FileStore#download_safe → New safe version. Will return nil.
```
**Desired end-state:**
```
FileStore#download → New safe version. Will return nil.
FileStore#download! → New unsafe version. Will raise FileStore::DownloadError.
```
### What's next?
We need to do a quick audit of the call sites that are using the old unsafe version without any error handling, as well as check for call sites in plugins other repos. Follow-up PRs incoming.
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
Previously we hardcoded the DOWNLOAD_URL_EXPIRES_AFTER_SECONDS const
inside S3Helper to be 5 minutes (300 seconds). For various reasons,
some hosted sites may need this to be longer for other integrations.
The maximum expiry time for presigned URLs is 1 week (which is
604800 seconds), so that has been added as a validation on the
setting as well. The setting is hidden because 99% of the time
it should not be changed.
It's very easy to forget to add `require 'rails_helper'` at the top of every core/plugin spec file, and omissions can cause some very confusing/sporadic errors.
By setting this flag in `.rspec`, we can remove the need for `require 'rails_helper'` entirely.
