docs: public Request<List<Identity>> linkIdentity(String primaryUserId, String secondaryUserId, String provider, String connectionId) {
          Asserts.assertNotNull(primaryUserId, "primary user id");
          Asserts.assertNotNull(secondaryUserId, "secondary user id");
          Asserts.assertNotNull(provider, "provider");
  
          String url = baseUrl
                  .newBuilder()
                  .addPathSegments("api/v2/users")
                  .addPathSegment(primaryUserId)
                  .addPathSegment("identities")
                  .build()
                  .toString();
  
          CustomRequest<List<Identity>> request = new CustomRequest<>(client, url, "POST", new TypeReference<List<Identity>>() {
          });
          request.addHeader("Authorization", "Bearer " + apiToken);
          request.addParameter("provider", provider);
          request.addParameter("user_id", secondaryUserId);
          if (connectionId != null) {
              request.addParameter("connection_id", connectionId);
          }
          return request;
      }