Add the ability to pin Issues (#24406)

This adds the ability to pin important Issues and Pull Requests. You can
also move pinned Issues around to change their Position. Resolves #2175.

## Screenshots

![grafik](https://user-images.githubusercontent.com/15185051/235123207-0aa39869-bb48-45c3-abe2-ba1e836046ec.png)

![grafik](https://user-images.githubusercontent.com/15185051/235123297-152a16ea-a857-451d-9a42-61f2cd54dd75.png)

![grafik](https://user-images.githubusercontent.com/15185051/235640782-cbfe25ec-6254-479a-a3de-133e585d7a2d.png)

The Design was mostly copied from the Projects Board.

## Implementation
This uses a new `pin_order` Column in the `issue` table. If the value is
set to 0, the Issue is not pinned. If it's set to a bigger value, the
value is the Position. 1 means it's the first pinned Issue, 2 means it's
the second one etc. This is dived into Issues and Pull requests for each
Repo.

## TODO
- [x] You can currently pin as many Issues as you want. Maybe we should
add a Limit, which is configurable. GitHub uses 3, but I prefer 6, as
this is better for bigger Projects, but I'm open for suggestions.
- [x] Pin and Unpin events need to be added to the Issue history.
- [x] Tests
- [x] Migration

**The feature itself is currently fully working, so tester who may find
weird edge cases are very welcome!**

---------

Co-authored-by: silverwind <me@silverwind.io>
Co-authored-by: Giteabot <teabot@gitea.io>

web_src/js/features/repo-issue-list.js

@@ -2,6 +2,7 @@ import $ from 'jquery';
 import {updateIssuesMeta} from './repo-issue.js';
 import {toggleElem} from '../utils/dom.js';
 import {htmlEscape} from 'escape-goat';
+import {Sortable} from 'sortablejs';
 
 function initRepoIssueListCheckboxes() {
   const $issueSelectAll = $('.issue-checkbox-all');
@@ -119,8 +120,67 @@ function initRepoIssueListAuthorDropdown() {
   };
 }
 
+function initPinRemoveButton() {
+  for (const button of document.getElementsByClassName('pinned-issue-unpin')) {
+    button.addEventListener('click', async (event) => {
+      const el = event.currentTarget;
+      const id = Number(el.getAttribute('data-issue-id'));
+
+      // Send the unpin request
+      const response = await fetch(el.getAttribute('data-unpin-url'), {
+        method: 'delete',
+        headers: {
+          'X-Csrf-Token': window.config.csrfToken,
+          'Content-Type': 'application/json',
+        },
+      });
+      if (response.ok) {
+        // Delete the tooltip
+        el._tippy.destroy();
+        // Remove the Card
+        el.closest(`div.pinned-issue-card[data-issue-id="${id}"]`).remove();
+      }
+    });
+  }
+}
+
+async function pinMoveEnd(e) {
+  const url = e.item.getAttribute('data-move-url');
+  const id = Number(e.item.getAttribute('data-issue-id'));
+  await fetch(url, {
+    method: 'post',
+    body: JSON.stringify({id, position: e.newIndex + 1}),
+    headers: {
+      'X-Csrf-Token': window.config.csrfToken,
+      'Content-Type': 'application/json',
+    },
+  });
+}
+
+function initIssuePinSort() {
+  const pinDiv = document.getElementById('issue-pins');
+
+  if (pinDiv === null) return;
+
+  // If the User is not a Repo Admin, we don't need to proceed
+  if (!pinDiv.hasAttribute('data-is-repo-admin')) return;
+
+  initPinRemoveButton();
+
+  // If only one issue pinned, we don't need to make this Sortable
+  if (pinDiv.children.length < 2) return;
+
+  new Sortable(pinDiv, {
+    group: 'shared',
+    animation: 150,
+    ghostClass: 'card-ghost',
+    onEnd: pinMoveEnd,
+  });
+}
+
 export function initRepoIssueList() {
   if (!document.querySelectorAll('.page-content.repository.issue-list, .page-content.repository.milestone-issue-list').length) return;
   initRepoIssueListCheckboxes();
   initRepoIssueListAuthorDropdown();
+  initIssuePinSort();
 }