There is a race condition in DestroyGroupService now that projects are deleted asynchronously:

1. User attempts to delete group
2. DestroyGroupService iterates through all projects and schedules a Sidekiq job to delete each Project
3. DestroyGroupService destroys the Group, leaving all its projects without a namespace
4. Projects::DestroyService runs later but the can?(current_user,
   :remove_project) is `false` because the user no longer has permission to
   destroy projects with no namespace.
5. This leaves the project in pending_delete state with no namespace/group.

Projects without a namespace or group also adds another problem: it's not possible to destroy the container
registry tags, since container_registry_path_with_namespace is the wrong value.

The fix is to destroy the group asynchronously and to run execute directly on Projects::DestroyService.

Closes #17893

DRY code + fix rubocop

Add more test cases

Append to changelog

DRY changes list

find_url service for merge_requests

use GET for getting merge request links

remove files

rename to get_url_service

reduce loop

add test case for cross project

refactor tiny thing

update changelog

This change simplifies a Pipeline processing by introducing a special new status: created.
This status is used for all builds that are created for a pipeline.
We are then processing next stages and queueing some of the builds (created -> pending) or skipping them (created -> skipped).
This makes it possible to simplify and solve a few ordering problems with how previously builds were scheduled.
This also allows us to visualise a full pipeline (with created builds).

This also removes an after_touch used for updating a pipeline state parameters.
Right now in various places we explicitly call a reload_status! on pipeline to force it to be updated and saved.

Also, mutualize AccessRequests and Members endpoints for Group &
Project.
New API documentation for the AccessRequests endpoints.
Signed-off-by: NRémy Coutable <remy@rymai.me>

Instead of redirecting from the project service to the service and back to the model,
put all destruction code in the service. Also removes a possible source of failure
where run_after_commit may not destroy the project.

So we have raw_diffs too

This object will manage Gitlab::Git::Compare instances

Instead calling diff_collection.count use diff_collection.size which is cache on the diff_collection

Introducing the concept of SafeDiffs which relates 
diffs with UI highlighting.

If somehow a user attempted to accept a merge request that had
conflicts (e.g. the "Accept Merge Request" button or the MR itself was
not updated), `MergeService` did not properly detect that a conflict
occurred. It would assume that the MR went through without any issues
and close the MR as though everything was fine. This could cause
data loss if the source branch were removed.

Closes #20425

1. Instantiate `ProtectedBranchesAccessSelect` from `dispatcher`

2. Use `can?(user, ...)` instead of `user.can?(...)`

3. Add `DOWNTIME` notes to all migrations added in !5081.

4. Add an explicit `down` method for migrations removing the
   `developers_can_push` and `developers_can_merge` columns, ensuring that
   the columns created (on rollback) have the appropriate defaults.

5. Remove duplicate CHANGELOG entries.

6. Blank lines after guard clauses.

1. It makes sense to reuse these constants since we had them duplicated
   in the previous enum implementation. This also simplifies our
   `check_access` implementation, because we can use
   `project.team.max_member_access` directly.

2. Use `accepts_nested_attributes_for` to create push/merge access
   levels. This was a bit fiddly to set up, but this simplifies our code
   by quite a large amount. We can even get rid of
   `ProtectedBranches::BaseService`.

3. Move API handling back into the API (previously in
   `ProtectedBranches::BaseService#translate_api_params`.

4. The protected branch services now return a `ProtectedBranch` rather
   than `true/false`.

5. Run `load_protected_branches` on-demand in the `create` action, to
   prevent it being called unneccessarily.

6. "Masters" is pre-selected as the default option for "Allowed to Push"
   and "Allowed to Merge".

7. These changes were based on a review from @rymai in !5081.

1. This is a third line of defence (first in the view, second in the
   controller).

2. Duplicate the `API::Helpers.to_boolean` method in `BaseService`. The
   other alternative is to `include API::Helpers`, but this brings with it
   a number of other methods that might cause conflicts.

3. Return a 403 if authorization fails.

1. The new data model moves from `developers_can_{push,merge}` to
   `allowed_to_{push,merge}`.

2. The API interface has not been changed. It still accepts
   `developers_can_push` and `developers_can_merge` as options. These
   attributes are inferred from the new data model.

3. Modify the protected branch create/update services to translate from
   the API interface to our current data model.

1. Remove `master_or_greater?` and `developer_or_greater?` in favor of
   `max_member_access`, which is a lot nicer.

2. Remove a number of instances of `include Gitlab::Database::MigrationHelpers`
   in migrations that don't need this module. Also remove comments where
   not necessary.

3. Remove duplicate entry in CHANGELOG.

4. Move `ProtectedBranchAccessSelect` from Coffeescript to ES6.

5. Split the `set_access_levels!` method in two - one each for `merge` and
   `push` access levels.

1. So it works with the new data model for protected branch access levels.

1. Move to dropdowns instead of checkboxes. One each for "Allowed to
   Push" and "Allowed to Merge"

2. Refactor the `ProtectedBranches` coffeescript class into
   `ProtectedBranchesAccessSelect`.

3. Modify the backend to accept the new parameters.

1. Improve error handling while creating protected branches.

2. Modify coffeescript code so that the "Developers can *" checkboxes
   send a '1' or '0' even when using AJAX. This lets us keep the backend
   code simpler.

3. Use services for both creating and updating protected branches.
   Destruction is taken care of with `dependent: :destroy`

Refactor spam validation to a concern that can be easily reused and improve legibility in `SpamCheckService`

This reverts merge request !5375

Replace invocation of `find` with Ruby code that matches old cached
files in a better, and safe way to avoid data-integrity issues.

added spec for avatar saver

avatar saver!

added avatar restorer spec

fix spec

added avatar restorer class

fix export service

fix warnings, added changelog

fix spec

some refactoring based on feedback

fixed a few issues after testing i/e avatar