The following optimizations were performed:

- Add new association to GroupMember and ProjectMember

  This new association will allow us to check if a user is a member of a
  Project or Group through a single query instead of two.

- Optimize retrieving of Members when adding multiple Users

parent_id is being set to 0 by RSpec.

Sub groups should not have a visibility level higher than its parent.

If the project is in a group, the `group.refresh_members_authorized_projects`
is made non-blocking, and we call `current_user.refresh_authorized_projects`
directly.

Projects in a personal namespace are more difficult. Rather than passing the
`blocking:` parameter through the entire `add_master` chain, have the
`AuthorizedProjectsWorker` automatically inline authorizations for three IDs or
less. Since the maximum number of IDs in this path is 2, that has the same effect.

The `members` table can have entries where `user_id: nil`, because people can
invite group members by email. We never want to include those as members,
because it might cause confusion with the anonymous (logged out) user.

In EE, we make use of `namespace#public?` in projects. When the project is in a
personal namespace, this breaks as the `public?` helper isn't present.

Fix static-snalysis

Move the precedence of group secure variable before project secure variable. Allow project_id to be null.

Separate Ci::VariableProject and Ci::VariableGroup

Add the forgotton files

Add migration file to update type of ci_variables

Fix form_for fpr VariableProject

Fix test

Change the table structure according to the yorik advice

Add necessary migration files. Remove unnecessary migration spec.

Revert safe_model_attributes.yml

Fix models

Fix spec

Avoid self.variable. Use becomes for correct routing.

Use unique index on group_id and key

Add null: false for t.timestamps

Fix schema version

Rename VariableProject and VariableGroup to ProjectVariable and GroupVariable

Rename the rest of them

Add the rest of files

Basic BE change

Fix static-snalysis

Move the precedence of group secure variable before project secure variable. Allow project_id to be null.

Separate Ci::VariableProject and Ci::VariableGroup

Add the forgotton files

Add migration file to update type of ci_variables

Fix form_for fpr VariableProject

Fix test

Change the table structure according to the yorik advice

Add necessary migration files. Remove unnecessary migration spec.

Revert safe_model_attributes.yml

Fix models

Fix spec

Avoid self.variable. Use becomes for correct routing.

Use unique index on group_id and key

Add null: false for t.timestamps

Fix schema version

Rename VariableProject and VariableGroup to ProjectVariable and GroupVariable

Rename the rest of them

Add the rest of files

Implement CURD

Rename codes related to VariableGroup and VariableProject FE part

Remove unneccesary changes

Make Fe code up-to-date

Add protected flag to migration file

Protected group variables essential package

Update schema

Improve doc

Fix logic and spec for models

Fix logic and spec for controllers

 Fix logic and spec for views(pre feature)

Add feature spec

Fixed bugs. placeholder. reveal button. doc.

Add changelog

Remove unnecessary comment

godfat nice catches

Improve secret_variables_for arctecture

Fix spec

Fix StaticAnlysys & path_regex spec

Revert "Improve secret_variables_for arctecture"

This reverts commit c3216ca212322ecf6ca534cb12ce75811a4e77f1.

Use ayufan suggestion for secret_variables_for

Use find instead of find_by

Fix spec message for variable is invalid

Fix spec remove variable.group_id = group.id

godffat spec nitpicks

Use include Gitlab::Routing.url_helpers for presenter spec

This is allowed for existing instances so we don't end up 76 offenses
right away, but for new code one should _only_ use this if they _have_
to remove non database data. Even then it's usually better to do this in
a service class as this gives you more control over how to remove the
data (e.g. in bulk).

Previously, only group masters could do this. However, project reporters can
manage project labels, so there doesn't seem to be any need to restrict group
labels further.

Also, save a query or two by getting a single GroupMember object to find out if
the user is a master or not.

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.

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

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

Add `visibility` & `visibility=` methods to the
`Gitlab::VisibilityLevel` module so the `visibility_level` can be
get/set with a string value.

This reverts commit e00fb2bdc2090e9cabeb1eb35a2672a882cc96e9.

# Conflicts:
#	.rubocop.yml
#	.rubocop_todo.yml
#	lib/gitlab/ci/config/entry/global.rb
#	lib/gitlab/ci/config/entry/jobs.rb
#	spec/lib/gitlab/ci/config/entry/factory_spec.rb
#	spec/lib/gitlab/ci/config/entry/global_spec.rb
#	spec/lib/gitlab/ci/config/entry/job_spec.rb
#	spec/lib/gitlab/ci/status/build/factory_spec.rb
#	spec/lib/gitlab/incoming_email_spec.rb

This reverts commit cb10b725c8929b8b4460f89c9d96c773af39ba6b.

Before this commit, but still on this feature branch, the creation of
mattermost teams where a background job. However, it was decided it was
better that these happened as transaction so feedback could be displayed
to the user.