You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: system.rs
    path of file: ./repos/kanidm/server/testkit/tests
    
    the code of the file until where you have to start completion: use kanidm_client::KanidmClient;

/// This literally tests that the thing exists and responds in a way we expect, probably worth testing it better...
#[kanidmd_testkit::test]
async fn test_v1_system_post_attr(rsclient: KanidmClient) {
    let client = reqwest::ClientBuilder::new()
        .danger_accept_invalid_certs(true)
        .build()
        .unw
    
async fn test_v1_system_post_attr(rsclient: KanidmClient) {
    let client = reqwest::ClientBuilder::new()
        .danger_accept_invalid_certs(true)
        .build()
        .unwrap();

    let response = match client
        .post(rsclient.make_url("/v1/system/_attr/domain_name"))
        .json(&serde_json::json!({"filter": "self"}))
        .send()
        .await
    {
        Ok(value) => value,
        Err(error) => {
            panic!(
                "Failed to query {:?} : {:#?}",
                rsclient.make_url("v1/system/_attr/domain_name"),
                error
            );
        }
    };
    eprintln!("response: {:#?}", response);
    assert_eq!(response.status(), 422);

    let body = response.text().await.unwrap();
    eprintln!("{}", body);
}