set_first_user: try improving error reporting

Problem:

When there is an issue ("trying to use reserved username") it is reported as

> Anyhow(Backend call failed with status 422 and text '["There is a conflict between the entered\nusername and an existing username.\nTry another one."]')

(which is a wrapped `ServiceError::BackendError`)
even though the CLI is ready to handle a `ServiceError::WrongUser`

Solution:

let BaseHTTPClient::put return a deserialized response

but this commit still does not parse the JSON and does not convert the Err

rust/agama-lib/src/base_http_client.rs

@@ -129,15 +129,27 @@ impl BaseHTTPClient {
     ///
     /// * `path`: path relative to HTTP API like `/users/first`
     /// * `object`: Object that can be serialiazed to JSON as body of request.
-    pub async fn put(&self, path: &str, object: &impl Serialize) -> Result<(), ServiceError> {
-        let response = self.put_response(path, object).await?;
+    pub async fn put<T>(&self, path: &str, object: &impl Serialize) -> Result<T, ServiceError>
+    where
+        T: DeserializeOwned + std::fmt::Debug,
+    {
+        let response = self.request_response(reqwest::Method::PUT, path, object).await?;
         if response.status().is_success() {
-            Ok(())
+            if let Some(clen) = response.content_length() {
+                if clen == 0 {
+                    println!("empty body");
+                }
+            }
+
+            let ret = response.json::<T>().await.map_err(|e| e.into());
+            println!("PUT returns: {:#?}", ret);
+            ret
         } else {
             Err(self.build_backend_error(response).await)
         }
     }
 
+    /// FIXME redoc
     /// post object to given path and returns server response. Reports error only if failed to send
     /// request, but if server returns e.g. 500, it will be in Ok result.
     ///
@@ -147,13 +159,14 @@ impl BaseHTTPClient {
     ///
     /// * `path`: path relative to HTTP API like `/questions`
     /// * `object`: Object that can be serialiazed to JSON as body of request.
-    pub async fn put_response(
+    pub async fn request_response(
         &self,
+        method: reqwest::Method,
         path: &str,
         object: &impl Serialize,
     ) -> Result<Response, ServiceError> {
         self.client
-            .put(self.url(path))
+            .request(method, self.url(path))
             .json(object)
             .send()
             .await

rust/agama-lib/src/users/http_client.rs

@@ -25,9 +25,16 @@ impl UsersHttpClient {
         &self,
         first_user: &FirstUser,
     ) -> Result<(bool, Vec<String>), ServiceError> {
-        self.client.put("/users/first", first_user).await?;
-        // TODO: make BaseHTTPClient.put(_response) return the issues
-        Ok((true, vec!()))
+        let result: Result<Vec<String>, ServiceError> = self.client.put("/users/first", first_user).await;
+        if let Err(ServiceError::BackendError(422, ref issues_s)) = result {
+            // way to go:
+            // deserialize json from string
+            // and use (void) put
+            println!("ISSUUUS {}", issues_s);
+        }
+
+        let issues = result?;
+        Ok((issues.is_empty(), issues))
     }
 
     async fn root_config(&self) -> Result<RootConfig, ServiceError> {

rust/agama-server/src/users/web.rs

@@ -175,15 +175,17 @@ async fn set_first_user(
     // issues: for example, trying to use a system user id; empty password
     // success: simply !issues.is_empty()
     let (_success, issues) = state.users.set_first_user(&config).await?;
-    if issues.is_empty() {
-        Ok((StatusCode::NO_CONTENT, ().into_response()))
+    let status = if issues.is_empty() {
+        StatusCode::OK
     }
     else {
-        Ok((
-            StatusCode::UNPROCESSABLE_ENTITY,
-            Json(issues).into_response(),
-        ))
-    }
+        StatusCode::UNPROCESSABLE_ENTITY
+    };
+
+    Ok((
+        status,
+        Json(issues).into_response(),
+    ))
 }
 
 #[utoipa::path(get, path = "/users/first", responses(