Fix an incorrect form submission in repo-issue.js (#3675)

This fixes `initRepoPullRequestAllowMaintainerEdit()` to submit the form correctly (as a web form, rather than as JSON payload).

Fixes #3618, cherry picked from gitea#30854.

Co-Authored-By: wxiaoguang <wxiaoguang@gmail.com>

---

Manual testing steps:

- Open a PR against any repository, with the "Allow edits from maintainers" option checked.
- Open the developer console (`Ctrl-Shift-I` on Firefox), and look at the Network tab.
- Visit the PR, find the "Allow edits from maintainers" checkbox, and click it.
- See the developer console, and check that the response says the setting is false.
- Refresh the page *completely* (`Ctrl-Shift-R` on Firefox)
- Observe that the setting is off.
- Click the box again to enable it.
- See the developer console, and check that the response says the setting is true.
- Reload without cache again (`Ctrl-Shift-R` on Firefox)
- Observe that the setting is now on.

Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/3675
Reviewed-by: Earl Warren <earl-warren@noreply.codeberg.org>
Co-authored-by: Gergely Nagy <forgejo@gergo.csillger.hu>
Co-committed-by: Gergely Nagy <forgejo@gergo.csillger.hu>

release-notes/8.0.0/fix/3675.md

@@ -0,0 +1 @@
+Fixed an issue that rendered the "Allow edits from maintainers" checkbox disfunctional, preventing people from turning it on.

web_src/js/features/repo-issue.js

@@ -298,23 +298,23 @@ export function initRepoPullRequestMergeInstruction() {
 export function initRepoPullRequestAllowMaintainerEdit() {
   const wrapper = document.getElementById('allow-edits-from-maintainers');
   if (!wrapper) return;
-
-  wrapper.querySelector('input[type="checkbox"]')?.addEventListener('change', async (e) => {
-    const checked = e.target.checked;
+  const checkbox = wrapper.querySelector('input[type="checkbox"]');
+  checkbox.addEventListener('input', async () => {
     const url = `${wrapper.getAttribute('data-url')}/set_allow_maintainer_edit`;
     wrapper.classList.add('is-loading');
-    e.target.disabled = true;
     try {
-      const response = await POST(url, {data: {allow_maintainer_edit: checked}});
-      if (!response.ok) {
+      const resp = await POST(url, {data: new URLSearchParams({allow_maintainer_edit: checkbox.checked})});
+      if (!resp.ok) {
         throw new Error('Failed to update maintainer edit permission');
       }
+      const data = await resp.json();
+      checkbox.checked = data.allow_maintainer_edit;
     } catch (error) {
+      checkbox.checked = !checkbox.checked;
       console.error(error);
       showTemporaryTooltip(wrapper, wrapper.getAttribute('data-prompt-error'));
     } finally {
       wrapper.classList.remove('is-loading');
-      e.target.disabled = false;
     }
   });
 }