Pull Request for Issue # .
Using the API for changing langugage overrides does not work
See https://docs.joomla.org/J4.x:Joomla_Core_APIs - Section Overrides Languages

Summary of Changes

OverrideModel: Wrong determination of client (site or admin)
OverridesController: Edit function did not exist, Save function did not use correct language/client
APIController: Delete needs modelstate

Testing Instructions

Do your own API calls on Language Override Operations

or use my Postman collection https://github.com/MacJoom/j4x-api-collection Section 5.3

Update: Use the updated collection from Alexandre Elise:

https://github.com/alexandreelise/j4x-api-collection

Example calls:
POST:
http://newrelease6-0.test/joomla-cms/api/index.php/v1/languages/overrides/site/de-DE
raw Body: {"key":"JTESTIT","override":"text"}

replace http://newrelease6-0.test with your url

Result:
{
"links": {
"self": "http://newrelease6-0.test/joomla-cms/api/index.php/v1/languages/overrides/site/de-DE"
},
"data": {
"type": "overrides",
"id": "JTESTIT",
"attributes": {
"value": "text"
}
}
}
GET:
http://newrelease6-0.test/joomla-cms/api/index.php/v1/languages/overrides/site/de-DE
Result:
{
"links": {
"self": "http://newrelease6-0.test/joomla-cms/api/index.php/v1/languages/overrides/site/de-DE"
},
"data": [
{
"type": "overrides",
"id": "JTESTIT",
"attributes": {
"value": "text"
}
}
],
"meta": {
"total-pages": 1
}
GET: (language id)
http://newrelease6-0.test/joomla-cms/api/index.php/v1/languages/overrides/site/de-DE/JTESTIT
Result:
{
"links": {
"self": "http://newrelease6-0.test/joomla-cms/api/index.php/v1/languages/overrides/site/de-DE/JTESTIT"
},
"data": {
"type": "overrides",
"id": "JTESTIT",
"attributes": {
"value": "JTestit Entry"
}
}
}

PATCH:
http://newrelease6-0.test/joomla-cms/api/index.php/v1/languages/overrides/site/de-DE/JTESTIT
{"key":"JTESTIT","override":"new text 5"}
Result:
{
"links": {
"self": "http://newrelease6-0.test/joomla-cms/api/index.php/v1/languages/overrides/site/de-DE/JTESTIT"
},
"data": {
"type": "overrides",
"id": "JTESTIT",
"attributes": {
"value": "new text 5"
}
}
}

DELETE:
http://newrelease6-0.test/joomla-cms/api/index.php/v1/languages/overrides/site/de-DE/JTESTIT

Empty result: Status 204, Language Override is deleted

if you get Forbidden as result your Authorization is not set up correctly
use Auth Type: API Key
Key: X-Joomla-Token
Value: <copy from User Tab 'Joomla API Token'>

Actual result BEFORE applying this Pull Request

POST, PATCH and DEL requests fail

Expected result AFTER applying this Pull Request

All requests work

Link to documentations

Please select:

• Documentation link for docs.joomla.org:

• [ x] No documentation changes for docs.joomla.org needed

• Pull Request link for manual.joomla.org:

• [x ] No documentation changes for manual.joomla.org needed