Mention notification request fails with 404

Describe the bug
Mention notification request fails with 404

To Reproduce
Steps to reproduce the behavior:

1. Share Document between two users
2. mention other user in the document
3. Check console

Expected behavior
Mention notification in notification center

Screenshots

Request

{"mention":"alice"}

Response

{"message":"Notification already present"}

• Response says notification already present but I don't see notification in alice's account

Server details

Nextcloud version: latest master

Version of the richdocuments app: latest main

Version of Collabora Online: latest master

Browser log

21:16:29.125 Uncaught (in promise) 
Object { stack: "Y@http://nextcloud.local/apps-extra/richdocuments/js/richdocuments-viewer.js:2:631251\nLe@http://nextcloud.local/apps-extra/richdocuments/js/richdocuments-viewer.js:2:642671\nf@http://nextcloud.local/apps-extra/richdocuments/js/richdocuments-viewer.js:2:647347\nEventHandlerNonNull*715/We</<@http://nextcloud.local/apps-extra/richdocuments/js/richdocuments-viewer.js:2:647606\n715/We<@http://nextcloud.local/apps-extra/richdocuments/js/richdocuments-viewer.js:2:646935\nvt@http://nextcloud.local/apps-extra/richdocuments/js/richdocuments-viewer.js:2:654052\n_request@http://nextcloud.local/apps-extra/richdocuments/js/richdocuments-viewer.js:2:656879\nrequest@http://nextcloud.local/apps-extra/richdocuments/js/richdocuments-viewer.js:2:655406\n715/</t/<@http://nextcloud.local/apps-extra/richdocuments/js/richdocuments-viewer.js:2:657327\n715/a/<@http://nextcloud.local/apps-extra/richdocuments/js/richdocuments-viewer.js:2:625550\nuiMention@http://nextcloud.local/apps-extra/richdocuments/js/richdocuments-viewer.js:2:1865049\npostMessageHandler@http://nextcloud.local/apps-extra/richdocuments/js/richdocuments-viewer.js:2:1872920\ne.prototype.handlePostMessage/<@http://nextcloud.local/apps-extra/richdocuments/js/richdocuments-viewer.js:2:1841416\ne.prototype.handlePostMessage@http://nextcloud.local/apps-extra/richdocuments/js/richdocuments-viewer.js:2:1841272\ne/<@http://nextcloud.local/apps-extra/richdocuments/js/richdocuments-viewer.js:2:1840247\nEventListener.handleEvent*e@http://nextcloud.local/apps-extra/richdocuments/js/richdocuments-viewer.js:2:1840205\nmounted@http://nextcloud.local/apps-extra/richdocuments/js/richdocuments-viewer.js:2:1867918\nZt@http://nextcloud.local/apps-extra/viewer/js/logger-CYBBkF-8.chunk.mjs:2:26639\nbt@http://nextcloud.local/apps-extra/viewer/js/logger-CYBBkF-8.chunk.mjs:2:34555\ninsert@http://nextcloud.local/apps-extra/viewer/js/logger-CYBBkF-8.chunk.mjs:2:37998\nj@http://nextcloud.local/apps-extra/viewer/js/logger-CYBBkF-8.chunk.mjs:2:58724\nKg/<@http://nextcloud.local/apps-extra/viewer/js/logger-CYBBkF-8.chunk.mjs:2:60077\nbh/e.prototype._update@http://nextcloud.local/apps-extra/viewer/js/logger-CYBBkF-8.chunk.mjs:2:32129\nn@http://nextcloud.local/apps-extra/viewer/js/logger-CYBBkF-8.chunk.mjs:2:32899\ne.prototype.get@http://nextcloud.local/apps-extra/viewer/js/logger-CYBBkF-8.chunk.mjs:2:29101\ne.prototype.run@http://nextcloud.local/apps-extra/viewer/js/logger-CYBBkF-8.chunk.mjs:2:29838\n_h@http://nextcloud.local/apps-extra/viewer/js/logger-CYBBkF-8.chunk.mjs:2:35116\nqr/<@http://nextcloud.local/apps-extra/viewer/js/logger-CYBBkF-8.chunk.mjs:2:27659\nDs@http://nextcloud.local/apps-extra/viewer/js/logger-CYBBkF-8.chunk.mjs:2:27071\npromise callback*Hn@http://nextcloud.local/apps-extra/viewer/js/logger-CYBBkF-8.chunk.mjs:2:27159\nqr@http://nextcloud.local/apps-extra/viewer/js/logger-CYBBkF-8.chunk.mjs:2:27721\ncu@http://nextcloud.local/apps-extra/viewer/js/logger-CYBBkF-8.chunk.mjs:2:35628\ne.prototype.update@http://nextcloud.local/apps-extra/viewer/js/logger-CYBBkF-8.chunk.mjs:2:29774\ne.prototype.notify@http://nextcloud.local/apps-extra/viewer/js/logger-CYBBkF-8.chunk.mjs:2:9524\nset@http://nextcloud.local/apps-extra/viewer/js/logger-CYBBkF-8.chunk.mjs:2:11412\nii/ua.set@http://nextcloud.local/apps-extra/viewer/js/logger-CYBBkF-8.chunk.mjs:2:42532\nopenFileInfo@http://nextcloud.local/apps-extra/viewer/js/viewer-main.mjs:8:13980\nopenFile@http://nextcloud.local/apps-extra/viewer/js/viewer-main.mjs:8:13325\nasync*file@http://nextcloud.local/apps-extra/viewer/js/viewer-main.mjs:8:10283\nZt@http://nextcloud.local/apps-extra/viewer/js/logger-CYBBkF-8.chunk.mjs:2:26626\ne.prototype.run@http://nextcloud.local/apps-extra/viewer/js/logger-CYBBkF-8.chunk.mjs:2:29986\n_h@http://nextcloud.local/apps-extra/viewer/js/logger-CYBBkF-8.chunk.mjs:2:35116\nqr/<@http://nextcloud.local/apps-extra/viewer/js/logger-CYBBkF-8.chunk.mjs:2:27659\n", message: "Request failed with status code 404", name: "AxiosError", code: "ERR_BAD_REQUEST", config: {…}, request: XMLHttpRequest, response: {…}, status: 404 }
​
code: "ERR_BAD_REQUEST"
​
config: Object { timeout: 0, xsrfCookieName: "XSRF-TOKEN", xsrfHeaderName: "X-XSRF-TOKEN", … }
​
message: "Request failed with status code 404"
​
name: "AxiosError"
​
request: XMLHttpRequest { readyState: 4, timeout: 0, withCredentials: false, … }
​
response: Object { data: {…}, status: 404, statusText: "Not Found", … }
​
stack: "Y@http://nextcloud.local/apps-extra/richdocuments/js/richdocuments-viewer.js:2:631251\nLe@http://nextcloud.local/apps-extra/richdocuments/js/richdocuments-viewer.js:2:642671\nf@http://nextcloud.local/apps-extra/richdocuments/js/richdocuments-viewer.js:2:647347\nEventHandlerNonNull*715/We</<@http://nextcloud.local/apps-extra/richdocuments/js/richdocuments-viewer.js:2:647606\n715/We<@http://nextcloud.local/apps-extra/richdocuments/js/richdocuments-viewer.js:2:646935\nvt@http://nextcloud.local/apps-extra/richdocuments/js/richdocuments-viewer.js:2:654052\n_request@http://nextcloud.local/apps-extra/richdocuments/js/richdocuments-viewer.js:2:656879\nrequest@http://nextcloud.local/apps-extra/richdocuments/js/richdocuments-viewer.js:2:655406\n715/</t/<@http://nextcloud.local/apps-extra/richdocuments/js/richdocuments-viewer.js:2:657327\n715/a/<@http://nextcloud.local/apps-extra/richdocuments/js/richdocuments-viewer.js:2:625550\nuiMention@http://nextcloud.local/apps-extra/richdocuments/js/richdocuments-viewer.js:2:1865049\npostMessageHandler@http://nextcloud.local/apps-extra/richdocuments/js/richdocuments-viewer.js:2:1872920\ne.prototype.handlePostMessage/<@http://nextcloud.local/apps-extra/richdocuments/js/richdocuments-viewer.js:2:1841416\ne.prototype.handlePostMessage@http://nextcloud.local/apps-extra/richdocuments/js/richdocuments-viewer.js:2:1841272\ne/<@http://nextcloud.local/apps-extra/richdocuments/js/richdocuments-viewer.js:2:1840247\nEventListener.handleEvent*e@http://nextcloud.local/apps-extra/richdocuments/js/richdocuments-viewer.js:2:1840205\nmounted@http://nextcloud.local/apps-extra/richdocuments/js/richdocuments-viewer.js:2:1867918\nZt@http://nextcloud.local/apps-extra/viewer/js/logger-CYBBkF-8.chunk.mjs:2:26639\nbt@http://nextcloud.local/apps-extra/viewer/js/logger-CYBBkF-8.chunk.mjs:2:34555\ninsert@http://nextcloud.local/apps-extra/viewer/js/logger-CYBBkF-8.chunk.mjs:2:37998\nj@http://nextcloud.local/apps-extra/viewer/js/logger-CYBBkF-8.chunk.mjs:2:58724\nKg/<@http://nextcloud.local/apps-extra/viewer/js/logger-CYBBkF-8.chunk.mjs:2:60077\nbh/e.prototype._update@http://nextcloud.local/apps-extra/viewer/js/logger-CYBBkF-8.chunk.mjs:2:32129\nn@http://nextcloud.local/apps-extra/viewer/js/logger-CYBBkF-8.chunk.mjs:2:32899\ne.prototype.get@http://nextcloud.local/apps-extra/viewer/js/logger-CYBBkF-8.chunk.mjs:2:29101\ne.prototype.run@http://nextcloud.local/apps-extra/viewer/js/logger-CYBBkF-8.chunk.mjs:2:29838\n_h@http://nextcloud.local/apps-extra/viewer/js/logger-CYBBkF-8.chunk.mjs:2:35116\nqr/<@http://nextcloud.local/apps-extra/viewer/js/logger-CYBBkF-8.chunk.mjs:2:27659\nDs@http://nextcloud.local/apps-extra/viewer/js/logger-CYBBkF-8.chunk.mjs:2:27071\npromise callback*Hn@http://nextcloud.local/apps-extra/viewer/js/logger-CYBBkF-8.chunk.mjs:2:27159\nqr@http://nextcloud.local/apps-extra/viewer/js/logger-CYBBkF-8.chunk.mjs:2:27721\ncu@http://nextcloud.local/apps-extra/viewer/js/logger-CYBBkF-8.chunk.mjs:2:35628\ne.prototype.update@http://nextcloud.local/apps-extra/viewer/js/logger-CYBBkF-8.chunk.mjs:2:29774\ne.prototype.notify@http://nextcloud.local/apps-extra/viewer/js/logger-CYBBkF-8.chunk.mjs:2:9524\nset@http://nextcloud.local/apps-extra/viewer/js/logger-CYBBkF-8.chunk.mjs:2:11412\nii/ua.set@http://nextcloud.local/apps-extra/viewer/js/logger-CYBBkF-8.chunk.mjs:2:42532\nopenFileInfo@http://nextcloud.local/apps-extra/viewer/js/viewer-main.mjs:8:13980\nopenFile@http://nextcloud.local/apps-extra/viewer/js/viewer-main.mjs:8:13325\nasync*file@http://nextcloud.local/apps-extra/viewer/js/viewer-main.mjs:8:10283\nZt@http://nextcloud.local/apps-extra/viewer/js/logger-CYBBkF-8.chunk.mjs:2:26626\ne.prototype.run@http://nextcloud.local/apps-extra/viewer/js/logger-CYBBkF-8.chunk.mjs:2:29986\n_h@http://nextcloud.local/apps-extra/viewer/js/logger-CYBBkF-8.chunk.mjs:2:35116\nqr/<@http://nextcloud.local/apps-extra/viewer/js/logger-CYBBkF-8.chunk.mjs:2:27659\n"
​
status: 404
​
<prototype>: Object { constructor: Y(e, t, n, r, a), toJSON: toJSON(), stack: "", … }
uiMention.js:39:16

Start at uiMention.js:39:16 and reproduce the mention flow by sharing a document, mentioning another user, and checking the request and response. Trace the request behind the 404 and the “Notification already present” response; done means the mentioned user can see the notification in the notification center without the failed request.