Add index to labels for `type` and project_id`

Closes #27676

See merge request !8978

Fixed typo in slash commands docs

Closes #27674

See merge request !8976

When loading pages that display the number of open issues,
the backend runs a query such as:

```sql
SELECT "labels"."id" FROM "labels" WHERE "labels"."type" IN ('ProjectLabel') AND "labels"."project_id" = 1000
```

This results in an entire scan of the `labels` table. To optimize performance,
add the appropriate index to the table.

Closes #27676

Fix "NameError: uninitialized constant Rack::Proxy" in production environment

See merge request !8977

Fixes gitlab-org/gitlab-ce#27674

UX Guide: Button placement in groups

See merge request !8972

Integrate webpack for frontend asset compilation

Closes #14634

See merge request !7288

Document that the retro and kickoff notes are public

See merge request !8788

* master:
  Change window size before visiting page, to get correct scroll position
  Fix slash commands spec error
  Move project services to new location under Integrations
  Move webhooks to new a location under Integrations
  Fixed eslint test failure
  Fixed redirection from http://someproject.git to http://someproject
  Add traits for the different Event types to the Event factory
  prevent nonewline type diff lines from containing unfolding link
  ensure linenumber data attribute is correct for the last line in a diff chunk
  ensure last line in diff block is contained within a table row element
  ensure click event is bound only once

Resolve "Line numbers are off in dynamically loaded diff chunks"

Closes #26300

See merge request !8428

Change window size before visiting page, to get correct scroll position

See merge request !8963

Fix slash commands spec error

See merge request !8968

Redirect http://someproject.git to http://someproject

Closes #26275

See merge request !8951

Refactor integrations page documentation

See merge request !8966

Fixed eslint test failure

See merge request !8964

Merge branch '26825-diff-unfolding-within-merge-request-changes-tab-triggers-two-ajax-requests' into 'master'

Resolve diff unfolding redundant ajax request

Closes #26825

See merge request !8630

Prevent "nonewline" type diff lines from showing a diff unfolding link

Closes #26829

See merge request !8632

* master: (181 commits)
  Fixed adding to list bug
  Remove unnecessary queries for .atom and .json in Dashboard::ProjectsController#index
  Fixed modal lists dropdown not updating when list is deleted
  Fixed remove btn error after creating new issue in list
  Removed duplicated test
  Removed Masonry, instead uses groups of data
  Uses mixins for repeated functions
  Fixed up specs
  Props use objects with required & type values
  Removes labels instead of closing issue when clicking remove button
  Fixed JS lint errors
  Fixed issue card spec
  Added webkit CSS properties
  Fixed bug with empty state showing after search Fixed users href path being incorrect
  Fixed bug where 2 un-selected issues would stay on selected tab
  Fixed DB schema Changed how components are added in objects
  Added remove button
  Add optional id property to the issue schema
  Fixed issue link href
  Disabled add issues button if no lists exist
  ...

Add traits for the different Event types to the Event factory

See merge request !8870

Remove Turbolinks

Closes #25624

See merge request !8570

Add issues to boards list

Closes #26205

See merge request !8737

Adds /target_branch slash command functionality for merge requests

Closes #23619

See merge request !7216

Remove unnecessary queries for .atom and .json in Dashboard::ProjectsController#index

Closes #27267

See merge request !8956

replace words user(s) with member(s)

Closes #25460

See merge request !8872

Merge branch '27332-mini-pipeline-graph-with-many-stages-has-no-line-spacing-in-firefox-and-safari' into 'master'

Resolve "Mini pipeline graph with many stages has no line spacing in Firefox and Safari"

Closes #27332

See merge request !8886

Resolve "Rename "Builds" to "Pipelines", "CI/CD Pipelines", or "Jobs" everywhere"

Closes #17662

See merge request !8787

Improved ref switcher dropdown performance

Closes #18202

See merge request !7239