We don't need to find the filename from the remote URL

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

Specifically, the `ListAllMyBuckets` permission.

This works if you know the directory exists.

See more:

* https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/23981
* https://stackoverflow.com/a/12288581/1992201

Extract code to make it easier reusable
- introduce AttributesRewriter and ContentRewriter
  - support group entites when rewriting content
- make Uploader copy_to working for Namespaces

Sean McGivern authored Mar 02, 2018 and Micael Bergeron committed Mar 08, 2018

File uploads on objects storage should use hashed storage

Closes #4952

See merge request gitlab-org/gitlab-ee!4597

This reverts commit 54a575f1, reversing
changes made to c63af942.

Move uploads to object storage

Closes #4163

See merge request gitlab-org/gitlab-ee!3867

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

DJ Mountney authored Jun 07, 2017 and Bob Van Landuyt :neckbeard: committed Jun 08, 2017

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.

Handle videos in:
- MD preview in notes: commit, issue/MR, MR diff
- New notes in: commit, issue/MR, MR diff
- Persisted notes in: commit, issue/MR, MR diff

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

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