docs: public String save() {
          JsonObject state = new JsonObject()
              .add("accessToken", this.accessToken)
              .add("refreshToken", this.refreshToken)
              .add("lastRefresh", this.lastRefresh)
              .add("expires", this.expires)
              .add("userAgent", this.userAgent)
              .add("tokenURL", this.tokenURL)
              .add("baseURL", this.baseURL)
              .add("baseUploadURL", this.baseUploadURL)
              .add("autoRefresh", this.autoRefresh)
              .add("maxRequestAttempts", this.maxRequestAttempts);
          return state.toString();
      }