code: public String buildUrl(String clientId, String redirectUri, String[] scope, Setup setup) {
  
          String url = setup.getEnvironment() + "/oauth/authorize";
  
          url += String.format("?response_type=code&client_id=%s&redirect_uri=%s&scope=", clientId, redirectUri);
  
          for (Integer index = 0; index < scope.length; ++index) {
  
              url += scope[index];
  
              if ((index + 1) < scope.length) url += ',';
          }
          return url;
      }
docs: This method is used to build the URL to request access permission for your seller.
  
  @param   clientId
  {@code String} the APP ID.
  
  @param   redirectUri
  {@code String} the address that you want to redirect your user after they grant the permission.
  
  @param   scope
  {@code String array} the array of permissions that you want to request.
  Ex: RECEIVE_FUNDS, MANAGE_ACCOUNT_INFO, TRANSFER_FUNDS...
  
  @param   setup
  {@code Setup} the setup object.
  
  @return  {@code String}