Add todo toggle event
## What does this MR do?
Adds a custom jQuery event `todo:toggle` to detect when a new todo is added so that the respective todo counters (header navigation and sidebar) can update as needed
## Are there points in the code the reviewer needs to double check?
* I wasn't sure whether each `spec` should be modularized based on the html templates or whether they should be separated based on function. There are some crossovers between the `dashboard_spec` and the `header_spec`.
* The naming conventions for `sidebar` and `right_sidebar` were a little confusing since they were named the opposite in their `specs`. I made a few assumptions and named a few files based on what I thought they should be named. I'd be happy to change it to something else though 😄
## Why was this MR needed?
This resolves an existing issue where the todo count on the sidebar would not update (until refresh) and refactors the existing methods that are used to update the todo counters (header navigation and sidebar)
## What are the relevant issue numbers?
Closes#20140
## Does this MR meet the acceptance criteria?
- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- Tests
- [x] Added for this feature/bug
- [x] All builds are passing
- [x] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [x] Branch has no merge conflicts with `master` (if you do - rebase it please)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)
See merge request !5724
Pass the remember_me option into the u2f form and support it while authenticating
## What does this MR do?
Adds remember me support in the u2f authentication, and makes sure the flag gets passed from the login form to the u2f form.
Based on the changes for the same thing done for regular 2fa: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/4369
## Why was this MR needed?
The remember me option wasn't working for u2f devices (yubikey)
## What are the relevant issue numbers?
Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/18103
See merge request !5918
17465 Fixed dropdown cursor key navigation
## What does this MR do?
This MR fixes the use of cursor/arrow/enter key events with search dropdowns, allowing a user to navigate up and down the list with the arrow keys and then select their item with the enter key.
It also applies some *minor* scroll user experience fixes, such as resetting the selected dropdown item every time it opens/closes (also stops multiple dropdowns conflicting) and forcing the dropdown scroll to scroll right to the top or bottom depending on whether they have selected the first or last item, respectively.
## Are there points in the code the reviewer needs to double check?
I would like someone with GitLab experience to check over whether this would harm any unique implementations of the GitLabDropdown or SearchAutocomplete.
## Why was this MR needed?
The current version has incorrectly behaving search dropdowns in the navbar, they either do not navigate using the keyboard or do not use the enter keystroke to select a highlighted item.
## What are the relevant issue numbers?
Fixes#17465.
Closes#20752.
Closes#21014.
**Contributes** to #20754.
## Screenshots (if relevant)

See merge request !4781
Added bootstrap dropdown event triggers to invoke the open and close methods of the dropdown, allowing for the binding of array key events
Added #17465 fix entry to CHANGELOG
Fixed multi-dropdown selected row index conflict
Fixed whitespace diff
Added padding to the dropdown content iterative scroll as well as new conditional scrolls to scroll all the way to the top when the first item of a list is selected and to scroll all the way to the bottom when the last item of a list is selected
Added conditionals to the enable and disable autocomplete methods to stop multiple invocations without any enabled/disabled state change
Fixes some incorrect firing of requests. The dropdown box was invoking a new query every time it closed and the GitLabDropdownRemote callback was invoking a new query which was causing the dropdown double render issue.
Added .selectable css class to dropdown list items that are not dividers or headers and altered selectors to account for that. Moved scroll padding Number to variable.
Removed unused method
Started Dropdown tests
Added fixture and began first test
Almost finished, navigation done, action and close needed
YAY. TESTS DONE.
Altered test and fixed click
started removing selectable class use
Fixed as reviewed
altered selection method
Fixed autocomplete shutting dropdown on arrow key use
patched XSS vulns
updated tests
f
Added click fixes
Notes are awardables
## What does this MR do?
Makes sure we can :thunder_cloud_rain: comments/notes.
## What are the relevant issue numbers?
Follows up upon !2901, depends on !3785Closes#3655
## Screenshots (if relevant)
TODO
See merge request !4291
- Move the `TwoFactorAuthsController`'s `new` action to `show`, since
the page is not used to create a single "two factor auth" anymore. We
can have a single 2FA authenticator app, along with any number of U2F
devices, in any combination, so the page will be accessed after the
first "two factor auth" is created.
- Add the `u2f` javascript library, which provides an API to the
browser's U2F implementation.
- Add tests for the JS components
- No longer depends on the "hidden checkbox".
- No longer depends on manually storing/restoring the scroll position.
Instead, we take advantage of jquery.scrollTo.
- Event-based.
- Simplifies the state-based styling.
Prior, any of the specified IDs could have been hijacked by a table of
contents header, breaking the tab functionality. For example, a `##
Notes` header would get the id `notes` and prevent the Discussion tab
from being activated.
Closes#3908
MergeRequest#show performance improvements
This is a first pass on improving the performance of the `MergeRequests#show` page. Notable changes:
- The "Commits" tab is loaded lazily, so the initial page load should be much faster for MRs with many commits.
- Relative timestamps via `timeago` are only initialized once per load instead of `O(n^2)`. This greatly improves frontend rendering times for a large number of commits.
- Refactored `User.find_for_commit` to use a single ARel-generated SQL query instead of the old method which resulted in one query, and could result in up to three.
See merge request !838