This commit introduces the usage of Common Table Expressions (CTEs) to
efficiently retrieve nested group hierarchies, without having to rely on
the "routes" table (which is an _incredibly_ inefficient way of getting
the data). This requires a patch to ActiveRecord (found in the added
initializer) to work properly as ActiveRecord doesn't support WITH
statements properly out of the box.

Unfortunately MySQL provides no efficient way of getting nested groups.
For example, the old routes setup could easily take 5-10 seconds
depending on the amount of "routes" in a database. Providing vastly
different logic for both MySQL and PostgreSQL will negatively impact the
development process. Because of this the various nested groups related
methods return empty relations when used in combination with MySQL.

For project authorizations the logic is split up into two classes:

* Gitlab::ProjectAuthorizations::WithNestedGroups
* Gitlab::ProjectAuthorizations::WithoutNestedGroups

Both classes get the fresh project authorizations (= as they should be
in the "project_authorizations" table), including nested groups if
PostgreSQL is used. The logic of these two classes is quite different
apart from their public interface. This complicates development a bit,
but unfortunately there is no way around this.

This commit also introduces Gitlab::GroupHierarchy. This class can be
used to get the ancestors and descendants of a base relation, or both by
using a UNION. This in turn is used by methods such as:

* Namespace#ancestors
* Namespace#descendants
* User#all_expanded_groups

Again this class relies on CTEs and thus only works on PostgreSQL. The
Namespace methods will return an empty relation when MySQL is used,
while User#all_expanded_groups will return only the groups a user is a
direct member of.

Performance wise the impact is quite large. For example, on GitLab.com
Namespace#descendants used to take around 580 ms to retrieve data for a
particular user. Using CTEs we are able to reduce this down to roughly 1
millisecond, returning the exact same data.

== On The Fly Refreshing

Refreshing of authorizations on the fly (= when
users.authorized_projects_populated was not set) is removed with this
commit. This simplifies the code, and ensures any queries used for
authorizations are not mutated because they are executed in a Rails
scope (e.g. Project.visible_to_user).

This commit includes a migration to schedule refreshing authorizations
for all users, ensuring all of them have their authorizations in place.
Said migration schedules users in batches of 5000, with 5 minutes
between every batch to smear the load around a bit.

== Spec Changes

This commit also introduces some changes to various specs. For example,
some specs for ProjectTeam assumed that creating a personal project
would _not_ lead to the owner having access, which is incorrect. Because
we also no longer refresh authorizations on the fly for new users some
code had to be added to the "empty_project" factory. This chunk of code
ensures that the owner's permissions are refreshed after creating the
project, something that is normally done in Projects::CreateService.

Use the EnforcedStyleForMultiline: no_comma option.
Signed-off-by: NRémy Coutable <remy@rymai.me>

+ The statistics parameter was already accepted
* This commit ensure that it is respected for GET /projects/:id endpoint
+ Add documentation of the parameter and update the example response for stats

Removed all the unnecessary include of `WaitForAjax` and `ApiHelpers` in the specs.
Removed unnecessary usage of `api:true`

FFaker can generate data that randomly break our test suite. This
simplifies our factories and use sequences which are more predictive.
Signed-off-by: NRémy Coutable <remy@rymai.me>

This is not a good idea to memoize `json_response` using an instance
variable because `rspec-retry` doesn't clear instance variables on
retries, only `let` variables.

This will avoid issues where retries would fail on a different line that
the original failure, blurrying what's the real failure.

Also, automatically add api: true to specs under
/spec/requests/(ci/)?api/, and include JsonHelpers in controller, request
and API specs.
Signed-off-by: NRémy Coutable <remy@rymai.me>

The API was returning 500 when `nil` is passed for the `import_url`.

In fact, it was `Gitlab::UrlSanitizer.valid?` which was throwing a
`NoMethodError` when `nil` value was passed.

This commit was about 6 commits before squashing, with the main goal to
make all tests green. Now, after pushing this commit we'll see what the
CI has to say about that.

The query parameter `membership` should be more self-explaining.

Instead of exposing the VisibilityLevel as Integer, expose it as
String `visibility` for Project and ProjectSnippet.

Filter queries also accept the `visibility` as String instead of
`visibility_level` as Integer.

Also remove the `public` boolean.

 Rename column in the database
 Rename fields related to import/export feature
 Rename API endpoints
 Rename documentation links
 Rename the rest of occurrences in the code
 Replace the images that contain the words "build succeeds" and docs referencing to them
 Make sure pipeline is green and nothing is missing.

updated doc images

renamed only_allow_merge_if_build_succeeds in projects and fixed references

more updates

fix some spec failures

fix rubocop offences

fix v3 api spec

fix MR  specs

fixed issues with partials

fix MR spec

fix alignment

add missing v3 to v4 doc

wip - refactor v3 endpoints

fix specs

fix a few typos

fix project specs

copy entities fully to V3

fix  entity error

more fixes

fix failing specs

fixed missing entities in V3 API

remove comment

updated code based on feedback

typo

fix spec

This reverts commit cb10b725c8929b8b4460f89c9d96c773af39ba6b.

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

It consolidates these endpoints:
 - /projects
 - /projects/owned
 - /projects/visible
 - /projects/starred
 - /projects/all

Into the /projects endpoint using query parameters.

The create and edit actions for projects had these parameters:

- `public` (optional) - if true same as setting `visibility_level = 20`
- `visibility_level` (optional)

Remove the `public` parameter to avoid contradiction.

Ports changes from https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/642 back into CE

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

This adds counters for build artifacts and LFS objects, and moves
the preexisting repository_size and commit_count from the projects
table into a new project_statistics table.

The counters are displayed in the administration area for projects
and groups, and also available through the API for admins (on */all)
and normal users (on */owned)

The statistics are updated through ProjectCacheWorker, which can now
do more granular updates with the new :statistics argument.

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