Allow resolving conflicts with non-ASCII chars

Closes #26214

See merge request !9937

Add nested groups documentation

Closes #28761

See merge request !9783

We wanted to check that the text could be encoded as JSON, because
conflict resolutions are passed back and forth in that format, so the
file itself must be UTF-8. However, all strings from the repository come
back without an encoding from Rugged, making them ASCII_8BIT.

We force to UTF-8, and reject if it's invalid. This still leaves the
problem of a file that 'looks like' UTF-8 (contains valid UTF-8 byte
sequences), but isn't. However:

1. If the conflicts contain the problem bytes, the user will see that
   the file isn't displayed correctly.
2. If the problem bytes are outside of the conflict area, then we will
   write back the same bytes when we resolve the conflicts, even though
   we though the encoding was UTF-8.

Resolve "Document U2F limitations with multiple URLs"

Closes #28277

See merge request !9300

Added issue boards re-ordering docs

See merge request !9924

Fix typo on Milestones show page. Fixes #29214

Closes #29214

See merge request !9913

Fix typo in doc/development/polling.md: `If-None-Modified` -> `If-None-Match`

See merge request !9957

Allow to override GITLAB_GIT_TEST_REPO_URL to specify a different gitlab-git-test repo

Closes #27551

See merge request !9945

Speed up the issues/filtered_search/dropdown_author feature spec

See merge request !9951

Add a test which would rollback db and migrate again

Closes #29106

See merge request !9908

[ci skip]

Display full project name with namespace upon deletion

Closes #29469

See merge request !9955

Signed-off-by: Rémy Coutable <remy@rymai.me>

Fixing two migrations that could not be rolled back

See merge request !9953

* Removes ambiguity when two projects exist with the same name

when rolling back from 9-0-stable to 8.17.3

Fix link togglers jumping to top

Closes #29414

See merge request !9943

Toggle long Project names

Closes #28187

See merge request !9501

[ci skip]

Preserve order by priority on issues board

See merge request !9939

[ci skip]

[ci skip]

[ci skip]

Add performance/scalability concerns to CONTRIBUTING.md

See merge request !8677

Fix first line markdown helper for user profile activity stream

Closes #29425

See merge request !9920

Fix intermittent spec failures in notify_spec.rb

See merge request !9935

Resolve "Cancel button misaligned in New Application page"

Closes #29441

See merge request !9933

Remove unused satellites config

See merge request !9919

We will set this to the dev mirror in GitLab CE and EE on dev.
Signed-off-by: Rémy Coutable <remy@rymai.me>

Syshook documentation updated

See merge request !9893

Added filtered search bar to issue boards

Closes #28312

See merge request !9757

Use google-protobuf 3.2.0.1

Closes #29084

See merge request !9932

Include instructions to update /etc/default/gitlab

See merge request !9925

Fix relative position calculation

Closes #29269

See merge request !9837

Fix #29414

Fix https://gitlab.com/gitlab-org/gitlab-ce/issues/29425