code: public Maybe<String> getValidScope(String scope, String clientId) {
          return DBManagerFactory.getInstance()
                  .findClientCredentials(clientId)
                  .map(creds -> getValidScopeByScope(scope, creds.getScope()));
      }
docs: Checks whether a scope is valid for a given client id.
  
  @param scope    oauth scope
  @param clientId client id
  @return the scope if it is valid, otherwise returns null