Use es6-promise package to avoid webpack warnings

See merge request !9215

Adds `.json` to the endpoint requested in order to avoid showing JSON

Closes #27932

See merge request !9105

Set max width for text in mini pipeline graph

Closes #27924

See merge request !9188

Remove inactive default email services

See merge request !8987

Add MySQL info in install requirements

See merge request !9230

[ci skip]

Feedback:
https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/8987#note_22938402

This reverts commit f2ed7cbc9b36b6ad9bcc714b271e98ead756b816.

This way we could reuse this pool for other migrations

Feedback:

* https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/8987#note_22923350
* https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/8987#note_22923365

by ourselves so that even if the setting has 1 connection
we could still use more connections.

Note that we no longer generate this by default.
This is for clearing legacy default data.

Introduce Gitlab::Database.with_connection_pool

See merge request !9192

Move /projects/fork/:id to /projects/:id/fork in V4 API

Closes #14492

See merge request !8940

Fix ActiveRecord connection leaks

Closes #27949 and gitlab-com/infrastructure#1139

See merge request !9109

Add discussion events to contributions calendar

Closes #22645

See merge request !8821

Display loading indicator when filtering ref switcher dropdown

Closes #27966

See merge request !9144

Add omniauth-oauth2-generic strategy

Closes #26744

See merge request !9048

Add GFM support to nested groups

See merge request !9184

Feedback:
https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/9192#note_23293693

See https://github.com/stefanpenner/es6-promise/issues/100

```
[WDS] Warnings while compiling.
./vendor/assets/javascripts/es6-promise.auto.js
Module not found: Error: Can't resolve 'vertx' in
'/Users/eric/Documents/gitlab/gitlab-development-kit/gitlab/vendor/assets/javascripts'
 @ ./vendor/assets/javascripts/es6-promise.auto.js 140:16-26
 @ ./app/assets/javascripts/application.js
 @ multi (webpack)-dev-server/client?http://localhost:3808
./application.js
```

Fix UX Guide apostrophe use for singular common nouns

See merge request !9190

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

Replace static fixture for behaviors/quick_submit_spec.js

See merge request !9086

Replace static fixture for merge_request_tabs_spec.js

See merge request !9172

Make deploy key not show in User's keys list

Closes #27480

See merge request !9024

- Allows configurable Single Sign On with most simple OAuth2 providers
- Adds documentation for the new strategy

Closes #26744

Remove deprecated templates endpoints in V4

Closes #22818

See merge request !8853

Add option to receive email notifications about your own activity

See merge request !8836