If you're using multi-tenancy, you need to pass in the
tenantId option to apply the proper theme.
An application can be created at https://your-fusionauth-server-url/admin/application.
For more information, follow the FusionAuth 5-minute setup guide.
In the OAuth settings for your application, configure the following.
- Redirect URL
- Enabled grants
- Make sure Authorization Code is enabled.