**Description**
PUT entities/items/{item_id}/sitelinks/{wiki_id}
Request payload:
```
{
"sitelink": {
"title": ...,
"badges": [ Q-ID, ... ] (optional)
},
"comment": ... (optional)
"tags": [ ... ] (optional)
"bot": false
}
```
**Acceptance criteria:**
- The respective successful responses should present the relevant data as a
stringJSON object -- similar to the responses of GET /entities/items/{item_id}/sitelinks/{wiki_id}.
- If a sitelink in the given wiki didn't exist before the successful request the response should use 201 code.
- If the request changed the existing sitelink, the response code should be 200.
**Error cases to consider**
<table>
<tr>
<th>
</th>
<th>HTTP response code</th>
<th>response payload</th>
</tr>
<tr>
<td>Item does not exist </td>
<td>404</td>
<td>
`"code": "item-not-found"`
`"message": "Could not find an item with the ID: {item_id}"`
</td>
</tr>
<tr>
<td>Invalid item ID </td>
<td>400</td>
<td>
`"code": "invalid-item-id"`
`"message": "Not a valid item ID: {item_id}"`
`"context": {"item": "{item-id}"}`
</td>
</tr>
<tr>
<td>Invalid wiki ID </td>
<td>400</td>
<td>
`{ "code": "invalid-wiki-id", "message": "Not a valid wiki ID: {wiki_ID}"}`
</td>
</tr>
<tr>
<td>Sitelink does not exist for wiki ID
TODO: check if intended; seems not needed for this route</td>
<td>400</td>
<td>
`{ "code": "sitelink-does-not-exist", "message": "Sitelink does not exist for wiki ID {wiki_ID}" }`
</td>
</tr>
<tr>
<td>Invalid edit tag</td>
<td>400</td>
<td>
`{ "code": "invalid-edit-tag", "message": "Invalid MediaWiki tag: {tag}" }`
</td>
</tr>
<tr>
<td>Comment too long</td>
<td>400</td>
<td>
`{"code": "comment-too-long", "message": "Comment must not be longer than {limit} characters"}`
</td>
</tr>
</table>
**Notes**
- Automated edit summaries to be of the form: TBD!
- client can provide additional edit metadata: mediawiki tags, edit summary text to append to the automated summary, and a bot edit flag, like in GET /entities/items/{item_id}/labels/{language_code}
- Handle HTTP conditional request headers as in PUT /entities/items/{item_id}/statements (double check!)
- Handle user authentication/authorization like in PUT /entities/items/{item_id}/statements
**Additional notes:**
How Action API handles it: https://www.wikidata.org/w/api.php?action=help&modules=wbsetsitelink