Bug: API Cannot Create Topics via /forums/topics in IPC v5 Beta 13

Status: Not a bug

Issue Summary

In Invision Power Community v5 Beta 13, attempting to create a new forum topic via the REST API (/forums/topics) results in a NO_FORUM (1F294/2) error, even when:

The forum ID is valid and retrieved from /forums/forums.
The API key has full permissions for forum access and posting.
The ACP settings allow topic creation in the targeted forum.
The request format follows the API documentation.

Steps to Reproduce

Retrieve a list of available forums using:
```
GET https://codenamejessica.com/api/forums/forums?key={API_KEY}
```
- Expected: A list of forums (including sub-forums like "Open Source Projects" with ID 78).
- Actual: The API returns the correct list, confirming the forum ID exists.

Attempt to create a new topic in a valid forum (ID 78) using:

POST https://codenamejessica.com/api/forums/topics?key={API_KEY}

Request Payload:

{
    "forum": 78,
    "title": "API Test Post",
    "post": "<p>This is a test post created via API.</p>",
    "author": 3,
    "author_name": "Blogger"
}

Expected: A new topic should be created in forum ID 78.

Actual: The API responds with:

{
    "errorCode": "1F294/2",
    "errorMessage": "NO_FORUM"
}

Test posting in parent forums (IDs 3 and 86)
- Attempted the same POST request with different valid parent forums.
- Result: API still returns NO_FORUM.
Verify API Key permissions in ACP
- Full permissions granted to the API Key.
- No forum restrictions preventing posting.
- Posting enabled for the selected forums.

Try posting via cURL

curl -X POST "https://codenamejessica.com/api/forums/topics?key={API_KEY}" \
-H "Content-Type: application/json" \
-d '{
    "forum": 78,
    "title": "API Test Post",
    "post": "<p>This is a test post created via API.</p>",
    "author": 3,
    "author_name": "Blogger"
}'

Still returns NO_FORUM.

Expected Behavior

The API should allow posting topics in forums where the API Key has full permissions.

Actual Behavior

The API consistently returns NO_FORUM, blocking all topic creation, even in parent forums.

Additional Observations

/forums/forums successfully retrieves Forum ID 78, meaning it exists and is accessible.
/forums/topics fails with NO_FORUM, suggesting a possible bug in the API's forum validation logic.
The same API calls worked in IPC v4 without issue.
This may be a regression or a permissions bug introduced in v5 Beta 13.

System Information

Software Version: IPC v5 Beta 13
Hosting: Self-hosted (codenamejessica.com)
REST API Authentication: API Key (Full permissions)
Tested With: cURL, Python requests library
Error Code: 1F294/2 - NO_FORUM

Suggested Fix

Investigate forum validation logic in /forums/topics.
Confirm whether API keys can create topics in v5.
Check if sub-forums require a different API method.
Ensure API respects ACP permissions for topic creation.

Request for Assistance

Would appreciate confirmation if API topic creation is working in v5 Beta 13 for others.
If this is a known issue, is there a planned fix in an upcoming release?