Closes #26145

Finished up autocomplete_sources action and added frontend to fetch data only when its needed

Added wait_for_ajax to specs

Fixed builds and improved the setup/destroy lifecycle

Changed global namespace and DRYed up loading logic

Added safety for accidentally loading data twice

Removed destroy as its not necessary and is messing with click events from a blur race condition

Created AutocompleteSourcesController and updated routes

Fixed @undefined from tabbing before load ends

Disable tabSelectsMatch until we have loaded data

Review changes

expand remaining non-explicit eslint-disable blocks and factor out globals when no-undef encountered

Closes #25540

Added special char test to the default beforeInsert callback. I removed the quotes from the milestone displayTpl and added a skip setting for emoji instance

Review changes

Without this fix it is possible that the autocomplete popup will stay open with the very first match, no matter if there is a match further in the string.

Closes #25119

This reverts merge request !6796

adds entry in CHANGELOG

no uninitialized variable and unnecessary if statement

formatting issue in CHANGELOG

resolves scss lint warings

cleanup: unnecessary css classes

adds css class that cleaned up by mistake

replaces snake_case variables name with camelCase

removes unnecessary css class and adds white color border for avatar

moves changelog entry from 8.13 to 8.14

remove bottom margin from avatar-inline

resolves lint warnings

rebased and moves changelog entry to 8.14

fixes avatar shifting on hover

adds entry at top of 8.14 section in CHANGELOG.md

calls sanitization for gl.utils

syncing changelog with master and created changelog files using cli

changes changelog title

Moved most of the functions that contained "window.doSomething" that were located at:
- app/assets/javascripts/application.js
To the following file:
- app/assets/javascripts/lib/utils/common_utils.js

The functions listed here:
- window.ajaxGet
- window.split
- window.extractLast
- window.rstrip
- window.disableButtonIfEmptyField
- window.disableButtonIfAnyEmptyField
- window.sanitize
- window.unbindEvents
- window.shiftWindow

Now will be accessible from the "gl.utils" namespace

Other improvements:
- Ensure slash commands autocomplete doesn't break when noteable_type is not given
- Slash commands: improve autocomplete behavior and /due command
- We don't display slash commands for note edit forms.
- Add tests for reply by email with slash commands
- Be sure to execute slash commands after the note creation in Notes::CreateService
Signed-off-by: NRémy Coutable <remy@rymai.me>

Some important things to note:

- commands are removed from noteable.description / note.note
- commands are translated to params so that they are treated as normal
  params in noteable Creation services
- the logic is not in the models but in the Creation services, which is
  the right place for advanced logic that has nothing to do with what
  models should be responsible of!
- UI/JS needs to be updated to handle notes which consist of commands
  only
- the `/merge` command is not handled yet

Other improvements:

- Don't process commands in commit notes and display a flash is note is only commands
- Add autocomplete for slash commands
- Add description and params to slash command DSL methods
- Ensure replying by email with a commands-only note works
- Use :subscription_event instead of calling noteable.subscribe
- Support :todo_event in IssuableBaseService
Signed-off-by: NRémy Coutable <remy@rymai.me>