Closes #55564
This is first discovered in #54739 (comment 122609857) that if both if: and only:
are used in a before_action or after_action or alike, if: is completely ignored.

It persist temporary personal snippets under
user/:id namespaces temporarily while creating
a upload record to track it. If an user gets removed
while it's still a tmp upload, it also gets removed.
If the tmp upload is sent, the upload gets moved to
personal_snippets/:id as before. The upload record
also gets updated to the new model type as well.

Enables frozen string for the following:

* app/controllers/*.rb
* app/controllers/admin/**/*.rb
* app/controllers/boards/**/*.rb
* app/controllers/ci/**/*.rb
* app/controllers/concerns/**/*.rb

Partially addresses #47424.

This whitelists all existing offenses for the various CodeReuse cops, of
which most are triggered by the CodeReuse/ActiveRecord cop.

The status is shown for
- The author of a commit when viewing a commit
- Notes on a commit (regular/diff)
- The user that triggered a pipeline when viewing a pipeline
- The author of a merge request when viewing a merge request
- The author of notes on a merge request (regular/diff)
- The author of an issue when viewing an issue
- The author of notes on an issue
- The author of a snippet when viewing a snippet
- The author of notes on a snippet
- A user's profile page
- The list of members of a group/user

this will remove the need make N queries (per-note) at the
cost of having to mark notes with an attribute

this opens up the possibility for other special roles for notes

Add a rubocop rule to check if a method 'redirect_to' is used without explicitly set 'status' in 'destroy' actions of controllers

Refactor snippets finder & dont return internal snippets for external users

See merge request !2094

Fix snippets visibility for show action - external users can not see internal snippets

See merge request !2087

Remove slash commands from Markdown preview and display their outcome next to
the text field.
Introduce new "explanation" block to our slash commands DSL.
Introduce optional "parse_params" block to slash commands DSL that allows to
process a parameter before it is passed to "explanation" or "command" blocks.
Pass path for previewing Markdown as "data" attribute instead of setting
a variable on "window".

This reverts commit cb10b725c8929b8b4460f89c9d96c773af39ba6b.

Apply the same spam checks to public snippets (either personal snippets
that are public, or public snippets on public projects) as to issues on
public projects.

This reverts commit 3e991230.

# Conflicts:
#	app/models/project.rb