it will also automatically prune empty directories for
`FileUploader`-based uploaders.

Ran:
 - git format-patch v9.2.2..v9.2.5 --stdout > patchfile.patch
 - git checkout -b 9-2-5-security-patch origin/v9.2.2
 - git apply patchfile.patch
 - git commit
 - [Got the sha ref for the commit]
 - git checkout -b upstream-9-2-security master
 - git cherry-pick <SHA of the patchfile commit>
 - [Resolved conflicts]
 - git cherry-pick --continue

Ran:
 - git format-patch v9.2.2..v9.2.5 --stdout > patchfile.patch
 - git checkout -b 9-2-5-security-patch origin/v9.2.2
 - git apply patchfile.patch
 - git commit
 - [Got the sha ref for the commit]
 - git checkout -b upstream-9-2-security master
 - git cherry-pick <SHA of the patchfile commit>
 - [Resolved conflicts]
 - git cherry-pick --continue

- Moves a duplicate `file_storage?` definition into the common
  `GitlabUploader` ancestor.
- Get the `uploads` base directory from a class method rather than
  hard-coding it where it's needed. This will be used in a subsequent MR
  to store Uploads in the database.
- Improves the specs for uploaders.

Fix for XSS vulnerability in SVG attachments

See https://dev.gitlab.org/gitlab/gitlabhq/merge_requests/2059

Signed-off-by: NRémy Coutable <remy@rymai.me>

* Registered video MIME types
* Currently supporting browser-supported formats with extensions that match the mime type

This attempts to get CarrierWave's uploader - `FileUploader` into test
harness using a factory. that makes it easier to build an instance of
it.

Along with !3435 it may be easier to use uploaders in tests

Signed-off-by: NDmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

This commit generalizes the image upload via drag and drop so it supports all files.
It also adds access control for these files.