Fixes active items being selectable

Enabled eslint

Toggle button text fix

Closes #343

Fix typo

See merge request !955

Change docs title to represent the edition

See merge request !961

[EE] Group members in project members view

See merge request !958

[ci skip] Update upgrade guide from GitLab CE to GitLab EE for 8.15

Following the steps from https://gitlab.com/gitlab-org/release-tools/blob/master/doc/release-candidates.md#creating-rc1.

See merge request !959

When the project has invitees, no group members were
returned due to a `user_id NOT IN (42, NULL)` query which
always returned [] since a `user_id` would be NULL, thus the condition
could never match.
Signed-off-by: Rémy Coutable <remy@rymai.me>

Closes #24122

Fix css lint

I merged [CE->EE](https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/953) with [failing css lint](https://gitlab.com/gitlab-org/gitlab-ee/builds/7216539), this is a fix.
It was caused by https://gitlab.com/gitlab-org/gitlab-ee/commit/d6d22a5dbd2ee04b59b2a80b3b6228575c3ea3ec on CE side.

@iamphill Please take a look if fixes are OK. If no, please send a separate MR to fix it.

See merge request !956

[ci skip]
Signed-off-by: Rémy Coutable <remy@rymai.me>

CE upstream

Unmerged paths:
  (use "git add/rm <file>..." as appropriate to mark resolution)

	both modified:   .gitlab-ci.yml
	deleted by them: app/assets/stylesheets/pages/admin.scss
	both modified:   app/assets/stylesheets/pages/issuable.scss
	both modified:   app/controllers/projects/issues_controller.rb
	both modified:   app/helpers/projects_helper.rb
	both modified:   config/routes/group.rb
	both modified:   doc/api/merge_requests.md
	both modified:   lib/api/users.rb
	both modified:   spec/controllers/projects/issues_controller_spec.rb
	both modified:   spec/finders/merge_requests_finder_spec.rb
	both modified:   spec/services/projects/create_service_spec.rb
	both modified:   spec/services/system_note_service_spec.rb

CE commits: https://gitlab.com/gitlab-org/gitlab-ce/compare/14046b9c734e5e6506d63276f39f3f9d770c3699...50a784482e997cc039015e24b37d3f8a01a9cd3e

See merge request !953

EE-specific changes for gitlab-org/gitlab-ee#1137

## Summary

- gitlab-org/gitlab-ee#1137 is a `technical debt` issue to clean up the EE protected branch access levels (for users and groups) implementation.
- Some of this cleanup bleeds over to code shared by CE and EE. This portion is covered in this CE merge request: gitlab-org/gitlab-ce!7821

## References

- Closes #1137 

## Tasks

-  [#1137/!7821/!927] Follow-up from restricting pushes / merges by group
    - [x]  Implementation
        - [x]  Prefer `validates` with `:uniqueness` option!
            - https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/645#note_16390918
        - [x]  Could this be moved into `ProtectedBranchAccess`?
            - https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/645#note_16391013
            - https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/645#note_16391018
            - https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/645#note_16391023
        - [x]  Please name controller action specs after the method and action: `describe "GET project_groups"`
            - https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/645#note_16391093
        - [x]  I think we need more extensive integration specs here
            - https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/645#note_16391229
        - [x]  Does this need to be a proc?
            - https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/645#note_17145530
    - [x]  Tests
        - [x]  CE Passing
        - [x]  EE Passing
    - [x]  Meta
        - [x]  CHANGELOG entry created
        - [x]  EE branch has no merge conflicts with EE `master`
        - [x]  CE branch has no merge conflicts with CE `master`
        - [x]  Squashed related commits together
    - [x]  Review
        - [x]  CE Endboss
        - [x]  EE Endboss
            - [x]  Break javascript, make sure integration specs catch the failure
    - [ ]  Merge
        - [x]  CE
        - [ ]  EE


See merge request !927

[ci skip]

[ci skip]