... automatically when it goes from false to true

unless explicitly unsubscribed

(also if service_desk_enabled is off)

for easier adding for EE

Resolve "Deleting a user shouldn't delete associated records"

See merge request !1581

Open new board after creating it

Closes gitlab-ce#29611

See merge request !1449

1. Have `MigrateToGhostUser` be a service rather than a mixed-in module, to keep
   things explicit. Specs testing the behavior of this class are moved into a
   separate service spec file.

2. Add a `user.reported_abuse_reports` association to make the
   `migrate_abuse_reports` method more consistent with the other `migrate_`
   methods.

elasticsearch: Add support for an experimental repository indexer

Closes #1606

See merge request !1483

Recent search history for issues -- EE merge edition

Closes gitlab-ce#27262

See merge request !1547

Linking to edit file directly -- EE merge edition

See merge request !1546

Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/27262

Conflicts:
	app/assets/javascripts/filtered_search/filtered_search_manager.js
	app/views/shared/issuable/_search_bar.html.haml

... when the user is destroyed.

1. Normally, for a given awardable and award emoji name, a user is only allowed
   to create a single award emoji.

2. This validation needs to be removed for ghost users, since:

   - User A and User B have created award emoji - with the same name and against
     the same awardable
   - User A is deleted. Their award emoji is moved to the ghost user
   - User B is deleted. Their award emoji needs to be moved to the ghost user.
     However, this breaks the uniqueness validation, since the ghost user is
     only allowed to have one award emoji of a given name for a given awardable

... when the user is destroyed.

To clarify, this regards abuse reports that the to-be-deleted user has _reported_.

Introduction
------------

1. The foreign key was not explicitly specified on the association.
2. The `AbuseReport` model contains two references to user - `reporter_id` and
   `user_id`
3. `user.abuse_report` is supposed to return the single abuse report where
   `user_id` refers to the given user.

Bug Description
---------------

1. `user.abuse_report` would return an abuse report where `reporter_id` referred
   to the current user, if such an abuse report was present.

2. This implies a slightly more serious bug as well:

   - Assume User A filed an abuse report against User B
   - We have an abuse report where `reporter_id` is User A and `user_id` is User B
   - If User A is updated (`user_a.block`, for example), the abuse report would
     also be updated, such that both `reporter_id` _and_ `user_id` point to User A.

Fix
---

Explicitly declare the foreign key `user_id` in the `has_one` declaration

... when the user is destroyed.

1. When the user is deleted.

2. Refactor out code relating to "migrating records to the ghost user" into a
   `MigrateToGhostUser` concern, which is tested using a shared example.