Resolve "Mini pipeline graph dropdown looks weird on Safari and hover does not work on firefox"

Closes #26018, #26004, and #26002

See merge request !8282

Do not override incoming webhook channel for mattermost and slack

Closes #25887

See merge request !8270

Monkey-patch StrongParameters for ::UploadedFile

Closes gitlab-ee#1451

See merge request !8299

Improve spec for resetting incoming email token

Closes #25614

See merge request !8296

Improve ProcessCommitWorker for large push payloads

Closes #25827

See merge request !8267

Fix errorcode 500 on slash commands

Closes #26013

See merge request !8285

[ci skip] Fix wrong release date for 8.15.0 on CHANGELOG

See merge request !8294

When processing push payloads we now schedule at most the 100 most
recent commits, instead of all commits that were in a payload. This
prevents one from overloading the system by pushing thousands if not
millions of commits in a single go.

Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/25827

Fix code that selects latest pipelines

Closes #25993 and #26031

See merge request !8286

Feedback:
https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/8286/diffs#note_20435082

Post username as property, not user_name

See merge request !8261

Feedback from Grzegorz

Feedback:
https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/8286/diffs#note_20433402

Fix state_event parameter to reopen an issue

Closes #25958

See merge request !8246

The name latest implies that it's reverse chronological,
and we did expect it that way.

https://gitlab.com/gitlab-org/gitlab-ce/issues/25993#note_20429761


> ok, I think markglenfletchera is correct in
> https://gitlab.com/gitlab-com/support-forum/issues/1394#note_20399939
> that `Project#latest_successful_builds_for` is giving oldest pipeline
> rather than latest pipeline. This is a ~regression introduced by !7333
> where `order(id: :desc)` was removed causing this. The offending change
> was:
> https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/7333/diffs#b22732e5f39e176c7c719fe485847d0fb0564275_92_108
>
> The confusion was caused by the `latest` name implication, which
> actually didn't order anything, and I think we should add `order(id:
> :desc)` to `Ci::Pipeline.latest` otherwise it's confusing that it's not
> actually ordered.


Closes #25993

Coverage was failing, so this could slip through the cracks

Add more images to issue creation from unresolved discussions

See merge request !8279

Fixed typo in test-and-deploy-ruby-application-to-heroku.md

See merge request !8236

[ci skip]

Change earlier to task_status_short to avoid titlebar line wraps

Closes #25941

See merge request !8275

Stops GFM special characters interfering with markdown tags

See merge request !8265

Add Gitaly to the architecture of the application

See merge request !8264

Slack docs [ci skip]

See merge request !8269

Resolve "Labels are not consistent on all pages"

Closes #25951

See merge request !8256

[ci skip]