Implement the http variant of the bank server.

During that process, many shortcomings with the socket server and the
bank lib were fixed.

I am aware a massive commit like this is not ideal.

http-server/src/handlers/close_account.rs

@@ -0,0 +1,29 @@
+use actix_web::{post, web, HttpResponse, Responder, Result};
+
+use bank::account::AccountError;
+use bank::bank::Bank;
+
+use crate::handlers::error::HttpAccountError;
+use crate::AppState;
+
+#[post("/{nr}/close")]
+pub async fn route(info: web::Path<String>, data: web::Data<AppState>) -> Result<impl Responder> {
+    let nr = info.into_inner();
+
+    info!("closing account {}...", nr);
+
+    let bank = data.bank.read().unwrap();
+    match Bank::account_action(bank, &nr, |account| {
+        // TODO: make the error handling part of the passivate method
+        if account.balance > 0_f64 {
+            Err(AccountError::AccountNotZero)
+        } else if account.passivate() {
+            Ok(0_f64)
+        } else {
+            Err(AccountError::Inactive)
+        }
+    }) {
+        Err(e) => Err(HttpAccountError(e).into()),
+        Ok(_) => Ok(HttpResponse::Ok().finish()),
+    }
+}