Bad request. A 400 response usually indicates invalid or missing required parameters, but can trigger for many reasons.
In this error example, the name given to a new client certificate already exists:
{
"detail": "Bad Request",
"errors": [
{}
],
"instance": "7cc378a1-ba9e-41a6-8255-27ee0a5a3897",
"problemId": "7cc378a1-ba9e-41a6-8255-27ee0a5a3897",
"status": 400,
"title": "Bad Request",
"type": "bad-request"
}