curl --request PATCH \
  --url https://{tenant}/api/apis/{apiId} \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/merge-patch+json' \
  --data '
{
  "api_definition": {
    "proxy": {
      "target_url": "https://httpbin.org/anything"
    }
  }
}
'

import requests

url = "https://{tenant}/api/apis/{apiId}"

payload = { "api_definition": { "proxy": { "target_url": "https://httpbin.org/anything" } } }
headers = {
    "Authorization": "Bearer <token>",
    "Content-Type": "application/merge-patch+json"
}

response = requests.patch(url, json=payload, headers=headers)

print(response.text)

const options = {
  method: 'PATCH',
  headers: {
    Authorization: 'Bearer <token>',
    'Content-Type': 'application/merge-patch+json'
  },
  body: JSON.stringify({api_definition: {proxy: {target_url: 'https://httpbin.org/anything'}}})
};

fetch('https://{tenant}/api/apis/{apiId}', options)
  .then(res => res.json())
  .then(res => console.log(res))
  .catch(err => console.error(err));

<?php

$curl = curl_init();

curl_setopt_array($curl, [
  CURLOPT_URL => "https://{tenant}/api/apis/{apiId}",
  CURLOPT_RETURNTRANSFER => true,
  CURLOPT_ENCODING => "",
  CURLOPT_MAXREDIRS => 10,
  CURLOPT_TIMEOUT => 30,
  CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
  CURLOPT_CUSTOMREQUEST => "PATCH",
  CURLOPT_POSTFIELDS => json_encode([
    'api_definition' => [
        'proxy' => [
                'target_url' => 'https://httpbin.org/anything'
        ]
    ]
  ]),
  CURLOPT_HTTPHEADER => [
    "Authorization: Bearer <token>",
    "Content-Type: application/merge-patch+json"
  ],
]);

$response = curl_exec($curl);
$err = curl_error($curl);

curl_close($curl);

if ($err) {
  echo "cURL Error #:" . $err;
} else {
  echo $response;
}

package main

import (
	"fmt"
	"strings"
	"net/http"
	"io"
)

func main() {

	url := "https://{tenant}/api/apis/{apiId}"

	payload := strings.NewReader("{\n  \"api_definition\": {\n    \"proxy\": {\n      \"target_url\": \"https://httpbin.org/anything\"\n    }\n  }\n}")

	req, _ := http.NewRequest("PATCH", url, payload)

	req.Header.Add("Authorization", "Bearer <token>")
	req.Header.Add("Content-Type", "application/merge-patch+json")

	res, _ := http.DefaultClient.Do(req)

	defer res.Body.Close()
	body, _ := io.ReadAll(res.Body)

	fmt.Println(string(body))

}

HttpResponse<String> response = Unirest.patch("https://{tenant}/api/apis/{apiId}")
  .header("Authorization", "Bearer <token>")
  .header("Content-Type", "application/merge-patch+json")
  .body("{\n  \"api_definition\": {\n    \"proxy\": {\n      \"target_url\": \"https://httpbin.org/anything\"\n    }\n  }\n}")
  .asString();

require 'uri'
require 'net/http'

url = URI("https://{tenant}/api/apis/{apiId}")

http = Net::HTTP.new(url.host, url.port)
http.use_ssl = true

request = Net::HTTP::Patch.new(url)
request["Authorization"] = 'Bearer <token>'
request["Content-Type"] = 'application/merge-patch+json'
request.body = "{\n  \"api_definition\": {\n    \"proxy\": {\n      \"target_url\": \"https://httpbin.org/anything\"\n    }\n  }\n}"

response = http.request(request)
puts response.read_body

{
  "Message": "Api updated",
  "Meta": null,
  "Status": "OK"
}

{
  "Message": "Merge patch must be a JSON object",
  "Meta": null,
  "Status": "Error"
}

{
  "ID": "<string>",
  "Message": "<string>",
  "Meta": "<unknown>",
  "Status": "<string>"
}

{
  "Message": "api definition does not exist",
  "Meta": null,
  "Status": "Error"
}

{
  "Message": "The API definition kept changing during the update: retry",
  "Meta": null,
  "Status": "Error"
}

{
  "Message": "The API definition has changed since it was read: read it again and retry",
  "Meta": null,
  "Status": "Error"
}

{
  "Message": "Merge patch is too large",
  "Meta": null,
  "Status": "Error"
}

{
  "Message": "Unsupported Content-Type: use application/merge-patch+json",
  "Meta": null,
  "Status": "Error"
}