if you send a POST request to /api/v1/patrons with the header
Content-Type: application/x-www-form-urlencoded

which is a default header for curl and libcurl with POST requests, by the way, then Koha will try to parse it as a JSON, which leads to questions like this https://stackoverflow.com/questions/68106741/post-koha-patrons-to-koha-lms-using-php-curl/70155185#70155185 and responses like this

```
{
    //Here is missing some code.
    "errors": [{
            "message": "Missing property.",
            "path": "/body/address"
        },
        {
            "message": "Missing property.",
            "path": "/body/category_id"
        },
        {
            "message": "Missing property.",
            "path": "/body/city"
        },
        {
            "message": "Missing property.",
            "path": "/body/library_id"
        },
        {
            "message": "Missing property.",
            "path": "/body/surname"
        }],
    "status": 400
}
```

while HTTP 400 is a pretty good response, the correct response for unsupported Content-Type is actually 

>HTTP/1.1 415 Unsupported Media Type

and the error message could be something like

{    "errors": [{
            "message": "request body must be application/json"
        }],
]