**//NOTE: This endpoint is deprecated. If there are no callers, we may not need to implement it. We should confirm whether or not this endpoint is needed before working on it. If the endpoint is not needed, we can close this task as Invalid.//**
**//NOTE: If we do need to keep this endpoint, we should check callers to see if we can remove the deprecated "id" value from the response//**
Create a REST handler and any other necessary associated code (extension.json entry, helper classes, etc.) for the `POST lists/{id}/entries` endpoint.
[] endpoint implemented
[] tests created
[] tests pass
**Endpoint summary:**
Create a new list entry.
**Endpoint description:**
Creates a new list entry in the given list. On conflict, does nothing and returns the data of an existing list.
The list must belong to the current user and the request must be authenticated with a MediaWiki session cookie.
Stability: [unstable](https://www.mediawiki.org/wiki/API_versioning#Unstable)
This endpoint is deprecated and might be removed without warning. Use the batch version instead.
**Associated RESTBase code**
[[ https://gerrit.wikimedia.org/r/plugins/gitiles/mediawiki/services/restbase/+/d544e9da48b9c79afb2338b7bab6960a94db6c61/v1/lists.yaml#530 | lists.yaml ]] (spec+forwarding)
[[ https://gerrit.wikimedia.org/g/mediawiki/services/restbase/+/d544e9da48b9c79afb2338b7bab6960a94db6c61/test/features/lists.js#798 | lists.js ]] (tests)
**Associated Action API code**
[[ https://gerrit.wikimedia.org/r/plugins/gitiles/mediawiki/extensions/ReadingLists/+/refs/heads/master/src/Api/ApiReadingListsCreateEntry.php#14 | ApiReadingListsCreateEntry ]]
[[ https://gerrit.wikimedia.org/r/plugins/gitiles/mediawiki/extensions/ReadingLists/+/refs/heads/master/tests/phpunit/Api/ApiReadingListsCreateEntryTest.php#17 | ApiReadingListsCreateEntryTest ]]
**Parameters:**
| name | source | required | type | example | default | possible values | description |
| id | path | yes | integer | 42 | N/A | N/A | |
| csrf_token | query | yes | string | f63c343876da566045e6b59c4532450559c828d3+\\ | N/A | N/A | The CRSF edit token provided by the MediaWiki API |
**Request Body:**
[[ https://gerrit.wikimedia.org/g/mediawiki/services/restbase/+/d544e9da48b9c79afb2338b7bab6960a94db6c61/v1/lists.yaml#955 | list_entry_write ]]
**Error Response**
#/components/schemas/problem per [[ https://gerrit.wikimedia.org/r/plugins/gitiles/mediawiki/services/restbase/+/refs/heads/master/doc/API.md | API.md ]] and [[ https://datatracker.ietf.org/doc/html/draft-nottingham-http-problem | draft-nottingham-http-problem ]]
**Success Response**
| value | type | description |
| id | integer | List entry ID. Deprecated, will be removed. Use the full entry object instead. |
| entry | object of [[ https://gerrit.wikimedia.org/g/mediawiki/services/restbase/+/d544e9da48b9c79afb2338b7bab6960a94db6c61/v1/lists.yaml#939 | list_entry_read ]] | |