code: public String registerScope(FullHttpRequest req) throws OAuthException {
          String contentType = (req.headers() != null) ? req.headers().get(HttpHeaderNames.CONTENT_TYPE) : null;
          // check Content-Type
          if (contentType != null && contentType.contains(ResponseBuilder.APPLICATION_JSON)) {
              try {
                  Scope scope = InputValidator.validate(req.content().toString(CharsetUtil.UTF_8), Scope.class);
                  if (scope.valid()) {
                      if (!Scope.validScopeName(scope.getScope())) {
                          LOG.error("scope name is not valid");
                          throw new OAuthException(SCOPE_NAME_INVALID_ERROR, HttpResponseStatus.BAD_REQUEST);
                      }
                      LOG.info(">>>>>>>>>>>>>>> scope = " + scope);
                      Scope foundScope = DBManagerFactory.getInstance().findScope(scope.getScope()).blockingGet();
                      if (foundScope != null) {
                          LOG.error("scope already exists");
                          throw new OAuthException(SCOPE_ALREADY_EXISTS, HttpResponseStatus.BAD_REQUEST);
                      } else {
                          // store in the DB, if already exists such a scope, overwrites it
                          DBManagerFactory.getInstance().storeScope(scope).blockingGet();
                      }
                  } else {
                      LOG.error("scope is not valid");
                      throw new OAuthException(MANDATORY_FIELDS_ERROR, HttpResponseStatus.BAD_REQUEST);
                  }
              } catch (Throwable e) {
                  LOG.error("cannot handle scope request", e);
                  throw new OAuthException(e, null, HttpResponseStatus.BAD_REQUEST);
              }
          } else {
              throw new OAuthException(ResponseBuilder.UNSUPPORTED_MEDIA_TYPE, HttpResponseStatus.BAD_REQUEST);
          }
          return SCOPE_STORED_OK_MESSAGE;
      }
docs: Register an oauth scope. If the scope already exists, returns an error.
  
  @param req http request
  @return String message that will be returned in the response