Sign up rate limit

web/src/app/Api.js

@@ -161,9 +161,10 @@ class Api {
             body: body
         });
         if (response.status === 409) {
-            throw new UsernameTakenError(username)
-        }
-        if (response.status !== 200) {
+            throw new UsernameTakenError(username);
+        } else if (response.status === 429) {
+            throw new AccountCreateLimitReachedError();
+        } else if (response.status !== 200) {
             throw new Error(`Unexpected server response ${response.status}`);
         }
     }
@@ -260,5 +261,9 @@ export class UsernameTakenError extends Error {
     }
 }
 
+export class AccountCreateLimitReachedError extends Error {
+    // Nothing
+}
+
 const api = new Api();
 export default api;