* add request review feature in pull request

add a way to notify specific reviewers to review like github , by add  or delet a  special type
review . The acton is  is similar to Assign ,  so many code reuse the function and items of
Assignee, but the meaning and result is different.

The Permission style is is similar to github, that only writer can add a review request from Reviewers,
but the poster can recall and remove a review request after a reviwer has revied even if he don't have
Write Premission. only manager , the poster and reviewer of a request review can remove it.

The reviewers can be requested to review contain all readers for private repo , for public, contain
all writers and watchers.

The offical Review Request will block merge if Reject can block it.

an other change: add ui otify for Assignees.

Co-authored-by: guillep2k <18600385+guillep2k@users.noreply.github.com>
Co-authored-by: Lauris BH <lauris@nix.lv>

Signed-off-by: a1012112796 <1012112796@qq.com>

* new change

* add placeholder string

* do some changes follow #10238 to add review requests num on lists also
change icon for review requests to eye

Co-authored-by: Lauris BH <lauris@nix.lv>

* [API] Add notification endpoints

 * add func GetNotifications(opts FindNotificationOptions)
 * add func (n *Notification) APIFormat()
 * add func (nl NotificationList) APIFormat()
 * add func (n *Notification) APIURL()
 * add func (nl NotificationList) APIFormat()
 * add LoadAttributes functions (loadRepo, loadIssue, loadComment, loadUser)
 * add func (c *Comment) APIURL()
 * add func (issue *Issue) GetLastComment()
 * add endpoint GET /notifications
 * add endpoint PUT /notifications
 * add endpoint GET /repos/{owner}/{repo}/notifications
 * add endpoint PUT /repos/{owner}/{repo}/notifications
 * add endpoint GET /notifications/threads/{id}
 * add endpoint PATCH /notifications/threads/{id}

* Add TEST

* code format

* code format

* Improve notifications

* batch load user

* Update notification only when read

* Fix reorder

* fix lint

* fix test

* fix lint

* make function meaningful

* fix comment

* Add 'mark all read' option to notifications

Signed-off-by: Sasha Varlamov <sasha@sashavarlamov.com>

* Fix exported comment

Signed-off-by: Sasha Varlamov <sasha@sashavarlamov.com>

* Format method comments

Signed-off-by: Sasha Varlamov <sasha@sashavarlamov.com>

* Fix exported comment

Signed-off-by: Sasha Varlamov <sasha@sashavarlamov.com>

Format method comments

Signed-off-by: Sasha Varlamov <sasha@sashavarlamov.com>

Tests for reactions (#3083)

* Unit tests for reactions

* Fix import order

Signed-off-by: Lauris Bukšis-Haberkorns <lauris@nix.lv>

Fix reaction possition when there is attachments (#3099)

Refactor notifications swap function

* Accept change to drop beforeupdate call

* Update purge notifications error message for consistency

* Drop unnecessary check for mark all as read button

* Remove debugging comment

* hide unactive on explore users and some refactors

* fix test for removed Organizations

* fix test for removed Organizations

* fix imports

* fix logic bug

* refactor the toConds

* Rename TestOrganizations to TestSearchUsers and add tests for users

* fix other tests

* fix other tests

* fix watchers tests

* fix comments and remove unused code

* Filter inactive users before sending emails or creating browser notifications

Signed-off-by: David Schneiderbauer <dschneiderbauer@gmail.com>

* fix formatting issues

Signed-off-by: David Schneiderbauer <dschneiderbauer@gmail.com>

* included requested changes

Signed-off-by: David Schneiderbauer <dschneiderbauer@gmail.com>

* optimized database queries

* rebasing new master and add tablenames for clarification in xorm queries

* remove escaped quotationmarks using backticks

Signed-off-by: David Schneiderbauer <dschneiderbauer@gmail.com>

* Fix tests code to prevent some runtime errors

* Reduce nesting

* Unit tests and remove unused functions in models/notification

* Read -> Unread