[PM-14484] ApiService showing html in error message (#14658)

* Make ApiService more testable

* Add ApiService tests

* Switch to only reading text/plain content

libs/angular/src/services/jslib-services.module.ts

@@ -337,6 +337,7 @@ import {
   CLIENT_TYPE,
   DEFAULT_VAULT_TIMEOUT,
   ENV_ADDITIONAL_REGIONS,
+  HTTP_OPERATIONS,
   INTRAPROCESS_MESSAGING_SUBJECT,
   LOCALES_DIRECTORY,
   LOCKED_CALLBACK,
@@ -700,6 +701,10 @@ const safeProviders: SafeProvider[] = [
     },
     deps: [ToastService, I18nServiceAbstraction],
   }),
+  safeProvider({
+    provide: HTTP_OPERATIONS,
+    useValue: { createRequest: (url, request) => new Request(url, request) },
+  }),
   safeProvider({
     provide: ApiServiceAbstraction,
     useClass: ApiService,
@@ -712,6 +717,7 @@ const safeProviders: SafeProvider[] = [
       LogService,
       LOGOUT_CALLBACK,
       VaultTimeoutSettingsService,
+      HTTP_OPERATIONS,
     ],
   }),
   safeProvider({