If I set the parameter "id" in the request body (see example below),
the value is set to the client. No new id value is generated for the client, which is the typically behavior of "Create a new role for the realm or client" and "Create a new user".

Is this a correct behavior?

Tested data example:
"Create Client":
"method":"POST","url":"<URL>:<PORT>/auth/admin/realms/<REALM>/clients"

"body":
"{
"id":"3",
"clientId":"testclient-3",
"name": "testclient-3",
"description": "TESTCLIENT-3",
"enabled": true,
"redirectUris":[ "\\" ],
"publicClient": true
}"

"headers":
[["Content-Type","application/json"],
["Authorization","Bearer <ACCESS_TOKEN>]]

Output for GET clients looks like:
 {
        "id": "3",
        "clientId": "testclient-3",
        "name": "testclient-3",
        "description": "TESTCLIENT-3",
        "surrogateAuthRequired": false,
        "enabled": true,
        "clientAuthenticatorType": "client-secret",
        "redirectUris":
        [
            "\"
        ],
        "webOrigins":
        [
        ],
        "notBefore": 0,
        "bearerOnly": false,
        "consentRequired": false,
        "serviceAccountsEnabled": false,
        "directGrantsOnly": false,
        "publicClient": true,
        "frontchannelLogout": false,
        "attributes":
        {
        },
...

Thanks a lot.

Best Regards,

Juraj