Search query is especially slow if a user searches a generic string
which matches many records, in such case search can take tens of
seconds or time out. To speed up the search query, we search only for
first 1000 records, if there is >1000 matching records we just display
"1000+" instead of precise total count supposing that with such amount
the exact count is not so important for the user.

Because for issues even limited search was not fast enough, 2-phase
approach is used for issues: first we use simpler/faster query to get
all public issues, if this exceeds the limit, we just return the limit.
If the amount of matching results is lower than limit, we re-run more
complex search query (which includes also confidential issues).
Re-running the complex query should be fast enough in such case because the
amount of matching issues is lower than limit.

Because exact total_count is now limited, this patch also switches to
to "prev/next" pagination.

Related #40540

For issuable models we keep two timestamps:
updated_at which is updated whenever any model attribute is changed,
last_edited_at which is changed when only title or description is
changed.

In UI bellow description we display who and when updated the item. But
last_edited_by (used for 'who') is mistakenly combined with updated_at
(when), last_edited_at should be used instead.

Closes #41247

Adds `#build_notification_recipients` to `NotificationRecipientService`
that returns the `NotificationRecipient` objects in order to be able to
access the new attribute `reason`.

This new attribute is used in the different notifier methods in order to
add the reason as a header: `X-GitLab-NotificationReason`.

Only the reason with the most priority gets sent.

We should use this limit everywhere, but especially in project search results,
where we could be highlighting very long single lines. (Typical examples:
minified JavaScript, and JSON data files.)

Closes #41561

Originally branch 'mk-toggle-writing-to-auth-keys-1631'

See merge request !2004

Squashed commits:
Add authorized_keys_enabled to Application Settings
Ensure default settings are exposed in UI
Without this change, `authorized_keys_enabled` is unchecked when it is nil, even if it should be checked by default.
Add “Speed up SSH operations” documentation
Clarify the reasons for disabling writes
Add "How to go back" section
Tweak copy
Update Application Setting screenshot

requests

Fix https://gitlab.com/gitlab-org/gitlab-ce/issues/33926

Changed file icons already addressed in
https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/15367

Closes #38741

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

- Create MemberPresenter alongside with GroupMemberPresenter and ProjectMemberPresenter
- Make Member model Presentable
- Move action_member_permission from MembersHelper into the MemberPresenter
- Added rspec using double, separate specs for GroupMemberPresenter and ProjectMemberPresenter

Fixes #28004.

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

Fixes project visibility guidelines

See merge request gitlab/gitlabhq!2226

(cherry picked from commit 877c42c0aaf3298d6001614c9706bc366ae4014c)

e4fd1c26 Ensure project wiki visibility guidelines are met

Moving the check out of the general requests, makes sure we don't have
any slowdown in the regular requests.

To keep the process performing this checks small, the check is still
performed inside a unicorn. But that is called from a process running
on the same server.

Because the checks are now done outside normal request, we can have a
simpler failure strategy:

The check is now performed in the background every
`circuitbreaker_check_interval`. Failures are logged in redis. The
failures are reset when the check succeeds. Per check we will try
`circuitbreaker_access_retries` times within
`circuitbreaker_storage_timeout` seconds.

When the number of failures exceeds
`circuitbreaker_failure_count_threshold`, we will block access to the
storage.

After `failure_reset_time` of no checks, we will clear the stored
failures. This could happen when the process that performs the checks
is not running.

Fix https://gitlab.com/gitlab-org/gitlab-ce/issues/40825

add a spec for commit merge request diff notes