code: public Request<ResourceServer> get(String resourceServerIdOrIdentifier) {
          Asserts.assertNotNull(resourceServerIdOrIdentifier, "Resource server ID");
  
          HttpUrl.Builder builder = baseUrl
                  .newBuilder()
                  .addPathSegments("api/v2/resource-servers")
                  .addPathSegment(resourceServerIdOrIdentifier);
  
          String url = builder.build().toString();
          CustomRequest<ResourceServer> request = new CustomRequest<>(client, url, "GET",
                  new TypeReference<ResourceServer>() {
                  });
          request.addHeader("Authorization", "Bearer " + apiToken);
          return request;
      }
docs: Cretes request for fetching single resource server by it's ID.
  See <a href=https://auth0.com/docs/api/management/v2#!/Resource_Servers/get_resource_servers_by_id>API documentation</a>
  
  @param resourceServerIdOrIdentifier {@link ResourceServer#id} or {@link ResourceServer#identifier} (audience) field
  @return request to execute