Revert MattermostNotificationService and SlackNotificationService to MattermostS…

Closes #25889

See merge request !8240

Fix RoutingError at ./spec/features/milestones/milestones_spec.rb

See merge request !8361

About GitLab link in sidebar that links to help page

Closes #24479

See merge request !8316

Check if user can read project before being assigned to issue

Closes #22664

See merge request !7980

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

Fix unclear closing issue behaviour on Merge Request show page

Closes #26152

See merge request !8345

Inherit permissions from parent group

See merge request !8071

fix left border in session tabs

Closes #24941

See merge request !8346

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

Merge branch '24820-buttons-in-the-branches-page-are-stacking-on-top-of-each-other-depending-on-the-selected-filter' into 'master'

Resolve "Buttons in the "Branches" page are stacking on top of each other depending on the selected filter"

Closes #24820

See merge request !8074

Fix instances where clicking a comment anchor twice will scroll to the wrong position

Closes #24876

See merge request !8046

Fix GFM dropdown not showing at beginning of new lines

Closes #26145

See merge request !8338

Refactor line length css

Closes #26153

See merge request !8354

Defer tooltip update on Resolve Comment button after DOM cycle

Closes #25957

See merge request !8335

Change status colors of runners to better defaults

Closes #25430

See merge request !8334

Replace link to Resolve conflicts with buttons

Closes #21135

See merge request !8229

Ensure javascript classes declared outside an IIFE are properties of window

See merge request !8080

adds kaminari_pagination controller concern with bounded pagination to not displ…

Closes #19988

See merge request !8172

darkened hr border color in descriptions because of update of bootstrap

See merge request !8333

Parameter already enforced via grape

See merge request !8344

Fix 500 error when visit group from admin area if group name contains dot

See merge request !8342

Cache project authorizations even when user has access to zero projects

Closes #26126

See merge request !8327

Revert MattermostNotificationService and SlackNotificationService to MattermostService and SlackService

Fix: Admin group show page does not work

Closes #26147

See merge request !8339

Use variables for display logic conditional checks

UX Guide: split state and action guidance for color

See merge request !8204

UX Guide: add moving transition animation guidance

See merge request !8147