Display existing worker configuration when already existing

Refs https://gitlab.com/arkindex/requests/-/issues/539

When a user tries to create a configuration that already exists (by name OR by content), an info (blue) notiifcation should be shown, saying "This configuration already exists named as 'XXX'".

If the backend does not gives the configuration details on conflict, a patch should be made and tied to that issue (giving a 400 code but with the payload)