adapters/application: Disable special case handling of 422 errors

The crate deletion endpoint is our first one that uses "422 Unprocessable Entity" HTTP errors, but it looks like Ember Data is expecting a slightly different layout for them. Since we don't need the special handling code in Ember Data, we can disable the extra code path and treat them like any other 4xx error.

app/adapters/application.js

@@ -3,6 +3,12 @@ import RESTAdapter from '@ember-data/adapter/rest';
 export default class ApplicationAdapter extends RESTAdapter {
   namespace = 'api/v1';
 
+  isInvalid() {
+    // HTTP 422 errors are causing all sorts of issues within Ember Data,
+    // so we disable their special case handling here, since we don't need/want it.
+    return false;
+  }
+
   handleResponse(status, headers, payload, requestData) {
     if (typeof payload === 'string') {
       try {