code: @Nullable
      public String getAuthorizationUrl() throws UnsupportedEncodingException {
          String authorizationCodeRequestUrl =
                  authorizationCodeFlow.newAuthorizationUrl().setScopes(scopes).build();
          if (redirectUri != null) {
              authorizationCodeRequestUrl += "&redirect_uri=" + URLEncoder.encode(redirectUri, "UTF-8");
          }
          return authorizationCodeRequestUrl;
      }
docs: Gets the authorization URL to retrieve the authorization code.